Enable go module support for go environment (#1152)

environments/go/Dockerfile-1.12

@@ -0,0 +1,24 @@
+ARG GO_VERSION=1.12.7
+
+FROM ubuntu:18.04 AS base
+WORKDIR /
+RUN apt update && apt install -y ca-certificates && rm -rf /var/lib/apt/lists/*
+
+FROM golang:${GO_VERSION} AS builder
+
+ENV GOPATH /usr
+ENV APP	   ${GOPATH}/src/github.com/fission/fission/environments/go
+
+WORKDIR ${APP}
+
+ADD context	    ${APP}/context
+ADD server.go   ${APP}
+
+RUN go get
+RUN go build -a -o /server server.go
+
+FROM base
+COPY --from=builder /server /
+
+ENTRYPOINT ["/server"]
+EXPOSE 8888

environments/go/builder/Dockerfile-1.12

@@ -0,0 +1,14 @@
+ARG BUILDER_IMAGE=fission/builder
+ARG GO_VERSION=1.12.7
+
+FROM ${BUILDER_IMAGE}
+
+FROM golang:${GO_VERSION}
+
+ENV GOPATH /usr
+ENV GO111MODULE on
+WORKDIR ${GOPATH}
+
+COPY --from=0 /builder /builder
+ADD build.sh /usr/local/bin/build
+

environments/go/builder/build.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 set -eux
 
@@ -6,6 +6,9 @@ srcDir=${GOPATH}/src/$(basename ${SRC_PKG})
 
 trap "rm -rf ${srcDir}" EXIT
 
+# http://ask.xmodulo.com/compare-two-version-numbers.html
+version_ge() { test "$(echo "$@" | tr " " "\n" | sort -rV | head -n 1)" == "$1"; }
+
 if [ -d ${SRC_PKG} ]
 then
     echo "Building in directory ${srcDir}"
@@ -18,4 +21,17 @@ then
 fi
 
 cd ${srcDir}
+
+if [ -f "go.mod" ]; then
+    if [ ! -z ${GOLANG_VERSION} ] && version_ge ${GOLANG_VERSION} "1.12"; then
+        go mod download
+    else
+        echo "Please update fission/go-builder and fission/go-env image to the latest version to support go module"
+        exit 1
+    fi
+else
+    # still need to do this; otherwise, go will complain "cannot find main module".
+    go mod init
+fi
+
 go build -buildmode=plugin -i -o ${DEPLOY_PKG} .