Fix Go 1.22 build, adapt to modules in KST repo

Resolves kaitai-io/kaitai_struct#1083

Depends on kaitai-io/kaitai_struct_tests@3749cac

src/go/1.21-linux-x86_64/Dockerfile

@@ -8,7 +8,7 @@ RUN ./prepare-alpine-init
 # Ruby is required for test infrastructure (aggregators, test result converters) to work
 RUN ./prepare-alpine-ruby
 
-# Required to download go-junit-report release in ./prepare-go-deps
+# Required to download go-junit-report release in ./prepare
 RUN apk add curl
 
 # Required for `go get` to work
@@ -25,3 +25,6 @@ RUN ./prepare
 # go version go1.21.3 linux/amd64
 
 RUN ./validate '^go version go1\.21\.'
+
+# Prevent Go from accessing the network (see https://go.dev/ref/mod#resolve-pkg-mod)
+ENV GOPROXY=off

src/go/1.22-linux-x86_64/Dockerfile

@@ -8,7 +8,7 @@ RUN ./prepare-alpine-init
 # Ruby is required for test infrastructure (aggregators, test result converters) to work
 RUN ./prepare-alpine-ruby
 
-# Required to download go-junit-report release in ./prepare-go-deps
+# Required to download go-junit-report release in ./prepare
 RUN apk add curl
 
 # Required for `go get` to work
@@ -25,3 +25,6 @@ RUN ./prepare
 # go version go1.22.0 linux/amd64
 
 RUN ./validate '^go version go1\.22\.'
+
+# Prevent Go from accessing the network (see https://go.dev/ref/mod#resolve-pkg-mod)
+ENV GOPROXY=off

src/go/_common/prepare

@@ -1,8 +1,16 @@
 #!/bin/sh -ef
 
-GO111MODULE=off go get -v github.com/kaitai-io/kaitai_struct_go_runtime/kaitai
-GO111MODULE=off go get -v github.com/stretchr/testify/assert
-GO111MODULE=off go get -v golang.org/x/text
+(
+git clone --depth 1 https://github.com/kaitai-io/kaitai_struct_go_runtime /download/runtime/go
+git -C /download/runtime/go rev-parse HEAD
+git clone --depth 1 https://github.com/kaitai-io/kaitai_struct_tests /download/tests
+cd /download/tests
+git rev-parse HEAD
+./prepare-go
+cd spec/go
+go mod download
+)
+rm -rf /download
 
 # Install https://github.com/jstemmer/go-junit-report
 curl -fsSL https://github.com/jstemmer/go-junit-report/releases/download/v2.1.0/go-junit-report-v2.1.0-linux-amd64.tar.gz | tar xzvf -