Merge pull request #1019 from traPtitech/dependabot/docker/golang-1.1…

…5.3-alpine

Bump golang from 1.15.2-alpine to 1.15.3-alpine

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.15.2-alpine AS build
+FROM golang:1.15.3-alpine AS build
 RUN apk add --update --no-cache git
 WORKDIR /go/src/github.com/traPtitech/traQ
 COPY ./go.* ./