diff --git a/.gitignore b/.gitignore
index c5601b6..4168218 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@
 *.dylib
 *.html
 .vscode/*
+.idea/
 
 # Test binary, built with `go test -c`
 *.test
diff --git a/Magefile.go b/Magefile.go
new file mode 100644
index 0000000..a1b2e94
--- /dev/null
+++ b/Magefile.go
@@ -0,0 +1,231 @@
+//+build mage
+
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+
+	"github.com/magefile/mage/mg"
+	"github.com/magefile/mage/sh"
+)
+
+var ldflags = ""
+
+// allow user to override go executable by running as GOEXE=xxx make ... on unix-like systems
+var goexe = "go"
+
+// Build is the default that fmt, vet, runs test and builds
+var Default = Build
+
+func init() {
+	if exe := os.Getenv("GOEXE"); exe != "" {
+		goexe = exe
+	}
+
+	// We want to use Go 1.11 modules even if the source lives inside GOPATH.
+	// The default is "auto".
+	os.Setenv("GO111MODULE", "on")
+}
+
+// Fmt run gofmt linter
+func Fmt() error {
+	if !isGoLatest() {
+		return nil
+	}
+	pkgs, err := packages()
+	if err != nil {
+		return err
+	}
+	failed := false
+	first := true
+	for _, pkg := range pkgs {
+		files, err := filepath.Glob(filepath.Join(pkg, "*.go"))
+		if err != nil {
+			return nil
+		}
+		for _, f := range files {
+			// gofmt doesn't exit with non-zero when it finds unformatted code
+			// so we have to explicitly look for output, and if we find any, we
+			// should fail this target.
+			s, err := sh.Output("gofmt", "-l", f)
+			if err != nil {
+				fmt.Printf("ERROR: running gofmt on %q: %v\n", f, err)
+				failed = true
+			}
+			if s != "" {
+				if first {
+					fmt.Println("The following files are not gofmt'ed:")
+					first = false
+				}
+				failed = true
+				fmt.Println(s)
+			}
+		}
+	}
+	if failed {
+		return errors.New("improperly formatted go files")
+	}
+	return nil
+}
+
+//  Vet run go vet linter
+func Vet() error {
+	if err := sh.Run(goexe, "vet", "./..."); err != nil {
+		return fmt.Errorf("error running go vet: %v", err)
+	}
+	return nil
+}
+
+// Run tests
+func Test() error {
+	env := map[string]string{"GOFLAGS": testGoFlags()}
+	return runCmd(env, goexe, "test", "./...", buildFlags(), "-tags", buildTags())
+}
+
+// TestRace run tests with race detector
+func TestRace() error {
+	env := map[string]string{"GOFLAGS": testGoFlags()}
+	return runCmd(env, goexe, "test", "-race", "./...", buildFlags(), "-tags", buildTags())
+}
+
+// TestCoverHTML generates test coverage report
+func TestCoverHTML() error {
+	const (
+		coverAll = "coverage-all.out"
+		cover    = "coverage.out"
+	)
+	f, err := os.Create(coverAll)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if _, err := f.Write([]byte("mode: count")); err != nil {
+		return err
+	}
+	pkgs, err := packages()
+	if err != nil {
+		return err
+	}
+	for _, pkg := range pkgs {
+		if err := sh.Run(goexe, "test", "-coverprofile="+cover, pkg); err != nil {
+			return err
+		}
+		b, err := ioutil.ReadFile(cover)
+		if err != nil {
+			if os.IsNotExist(err) {
+				continue
+			}
+			return err
+		}
+		idx := bytes.Index(b, []byte{'\n'})
+		b = b[idx+1:]
+		if _, err := f.Write(b); err != nil {
+			return err
+		}
+	}
+	if err := f.Close(); err != nil {
+		return err
+	}
+	return sh.Run(goexe, "tool", "cover", "-html="+coverAll)
+}
+
+// Build run linters, vet and tests
+func Build() error {
+	if strings.Contains(runtime.Version(), "1.8") {
+		// Go 1.8 doesn't play along with go test ./... and /vendor.
+		// We could fix that, but that would take time.
+		fmt.Printf("Skip Build on %s\n", runtime.Version())
+		return nil
+	}
+
+	// TODO: Add lint after fixing errors
+	mg.Deps(Fmt, Vet, TestRace)
+	return nil
+}
+
+var (
+	pkgPrefixLen = len("github.com/grafadruid/go-druid")
+	pkgs         []string
+	pkgsInit     sync.Once
+)
+
+// testGoFlags returns test flags that need to be set
+func testGoFlags() string {
+	return "-v"
+}
+
+func packages() ([]string, error) {
+	var err error
+	pkgsInit.Do(func() {
+		var s string
+		s, err = sh.Output(goexe, "list", "./...")
+		if err != nil {
+			return
+		}
+		pkgs = strings.Split(s, "\n")
+		for i := range pkgs {
+			pkgs[i] = "." + pkgs[i][pkgPrefixLen:]
+		}
+	})
+	return pkgs, err
+}
+
+func buildFlags() []string {
+	if runtime.GOOS == "windows" {
+		return []string{"-buildmode", "exe"}
+	}
+	return nil
+}
+
+func buildTags() string {
+	return "none"
+}
+
+func isGoLatest() bool {
+	return strings.Contains(runtime.Version(), "1.14")
+}
+
+func runCmd(env map[string]string, cmd string, args ...interface{}) error {
+	if mg.Verbose() {
+		return runWith(env, cmd, args...)
+	}
+	output, err := sh.OutputWith(env, cmd, argsToStrings(args...)...)
+	if err != nil {
+		fmt.Fprint(os.Stderr, output)
+	}
+
+	return err
+}
+
+func runWith(env map[string]string, cmd string, inArgs ...interface{}) error {
+	s := argsToStrings(inArgs...)
+	return sh.RunWith(env, cmd, s...)
+}
+
+func argsToStrings(v ...interface{}) []string {
+	var args []string
+	for _, arg := range v {
+		switch v := arg.(type) {
+		case string:
+			if v != "" {
+				args = append(args, v)
+			}
+		case []string:
+			if v != nil {
+				args = append(args, v...)
+			}
+		default:
+			panic("invalid type")
+		}
+	}
+
+	return args
+}
diff --git a/README.md b/README.md
index a0048bd..af0ad0e 100644
--- a/README.md
+++ b/README.md
@@ -3,3 +3,28 @@
 # go-druid
 A Golang client for Druid.
 Now supports Query API and Common API.
+
+### Development
+
+#### Testing
+`go-druid` uses mage to run tests locally.
+    Install Mage: 
+```    
+    git clone https://github.com/magefile/mage
+    cd mage
+    go run bootstrap.go
+```
+`mage -l` provides a list of targets that can be run. Default is `Check`
+
+```
+Targets:
+  build            runs go mod download and then installs the binary.
+  check*           run linters and tests
+  fmt              run gofmt linter
+  lint             run golint linter https://github.com/golang/lint
+  testCoverHTML    generates test coverage report
+  testRace         run tests with race detector
+  vet              run go vet linter
+
+* default target
+```
\ No newline at end of file
diff --git a/builder/query/group_by.go b/builder/query/group_by.go
index 61d90db..3d94e4e 100644
--- a/builder/query/group_by.go
+++ b/builder/query/group_by.go
@@ -23,7 +23,7 @@ type GroupBy struct {
 	PostAggregations []builder.PostAggregator `json:"postAggregations,omitempty"`
 	Having           builder.HavingSpec       `json:"having,omitempty"`
 	LimitSpec        builder.LimitSpec        `json:"limitSpec,omitempty"`
-	SubtotalsSpec    [][]string               `json:"subtotalsSpec",omitempty`
+	SubtotalsSpec    [][]string               `json:"subtotalsSpec,omitempty"`
 }
 
 func NewGroupBy() *GroupBy {
diff --git a/examples/tdigestExample.go b/examples/tdigestExample.go
index e4890a0..a4fe27a 100644
--- a/examples/tdigestExample.go
+++ b/examples/tdigestExample.go
@@ -33,7 +33,6 @@ func getConnection() *druid.Client {
 	To experiment, you can use the doubles_sketch_data.tsv file attached in this repo. It is a copy of  https://github.com/apache/druid/blob/master/extensions-contrib/tdigestsketch/src/test/resources/doubles_sketch_data.tsv
 */
 
-
 // tdigestSketchUsingBuilder example using Builder Pattern
 func tdigestSketchUsingBuilder() {
 	d := getConnection()
@@ -49,18 +48,16 @@ func tdigestSketchUsingBuilder() {
 	atds := aggregation.NewTDigestSketch().SetName("merged_sketch").SetFieldName("valuesTDS")
 	a := []builder.Aggregator{atds}
 
-
 	//TDigest Post Aggregation
 	qf := postaggregation.NewQuantilesFromTDigestSketchField().
 		SetType("fieldAccess").
 		SetFieldName("merged_sketch")
 	qa := postaggregation.NewQuantilesFromTDigestSketch().
 		SetField(qf).
-		SetFractions([]float64{0.25, 0.5, 0.75, 0.9, 0.95, 0.99}).  // add additional quantiles as needed
+		SetFractions([]float64{0.25, 0.5, 0.75, 0.9, 0.95, 0.99}). // add additional quantiles as needed
 		SetName("quantiles")
 	pa := []builder.PostAggregator{qa}
 
-
 	ts := query.NewTimeseries().SetDataSource(table).SetIntervals(is).SetAggregations(a).SetPostAggregations(pa).SetGranularity(m).SetLimit(10)
 	var results interface{}
 	_, err := d.Query().Execute(ts, &results)
diff --git a/go.mod b/go.mod
index 0d8faa8..53facbf 100644
--- a/go.mod
+++ b/go.mod
@@ -6,5 +6,6 @@ require (
 	github.com/davecgh/go-spew v1.1.1
 	github.com/google/go-querystring v1.0.0
 	github.com/hashicorp/go-retryablehttp v0.6.7
+	github.com/magefile/mage v1.11.0
 	github.com/stretchr/testify v1.2.2
 )
diff --git a/go.sum b/go.sum
index f3d8a04..93813bb 100644
--- a/go.sum
+++ b/go.sum
@@ -8,7 +8,37 @@ github.com/hashicorp/go-hclog v0.9.2 h1:CG6TE5H9/JXsFWJCfoIVpKFIkFe6ysEuHirp4DxC
 github.com/hashicorp/go-hclog v0.9.2/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
 github.com/hashicorp/go-retryablehttp v0.6.7 h1:8/CAEZt/+F7kR7GevNHulKkUjLht3CPmn7egmhieNKo=
 github.com/hashicorp/go-retryablehttp v0.6.7/go.mod h1:vAew36LZh98gCBJNLH42IQ1ER/9wtLZZ8meHqQvEYWY=
+github.com/magefile/mage v1.11.0 h1:C/55Ywp9BpgVVclD3lRnSYCwXTYxmSppIgLeDYlNuls=
+github.com/magefile/mage v1.11.0/go.mod h1:z5UZb/iS3GoOSn0JgWuiw7dxlurVYTu+/jHXqQg881A=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/lint v0.0.0-20201208152925-83fdc39ff7b5 h1:2M3HP5CCK1Si9FQhwnzYhXdG6DXeebvUHFpre8QvbyI=
+golang.org/x/lint v0.0.0-20201208152925-83fdc39ff7b5/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
+golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
+golang.org/x/mod v0.3.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7 h1:EBZoQjiKKPaLbPrbpssUfuHtwM6KV/vb4U85g/cigFY=
+golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/tools v0.1.0 h1:po9/4sTYwZU9lPhi1tOrb4hCv3qrhiQ77LZfGa2OjwY=
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+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=