Add go environment vendor directory support (#781)

* Add go environment vendor directory support
* Use symbolink instead of copying files to gopath
* Add go vendor example package & test

environments/go/builder/Dockerfile

@@ -5,9 +5,9 @@ FROM ${BUILDER_IMAGE}
 
 FROM golang:${GO_VERSION}
 
-COPY --from=0 /builder /builder
-
 ENV GOPATH /usr
+WORKDIR ${GOPATH}
 
+COPY --from=0 /builder /builder
 ADD build.sh /usr/local/bin/build
 

environments/go/builder/build.sh

@@ -1,19 +1,21 @@
 #!/bin/sh
 
+set -eux
+
+srcDir=${GOPATH}/src/$(basename ${SRC_PKG})
+
+trap "rm -rf ${srcDir}" EXIT
+
 if [ -d ${SRC_PKG} ]
 then
-    echo "Building in directory ${SRC_PKG}"
-    cd ${SRC_PKG}
-    go build -buildmode=plugin -i -o ${DEPLOY_PKG} .
+    echo "Building in directory ${srcDir}"
+    ln -sf ${SRC_PKG} ${srcDir}
 elif [ -f ${SRC_PKG} ]
 then
-    fn=$(basename ${SRC_PKG})
-    d=/tmp/$fn
-    mkdir $d
-    trap "rm -rf /tmp/$fn" EXIT
-    echo "Building file ${SRC_PKG} in $d"
-
-    cd $d
-    cp ${SRC_PKG} ./function.go
-    go build -buildmode=plugin -i -o ${DEPLOY_PKG} .
+    echo "Building file ${SRC_PKG} in ${srcDir}"
+    mkdir -p ${srcDir}
+    cp ${SRC_PKG} ${srcDir}/function.go
 fi
+
+cd ${srcDir}
+go build -buildmode=plugin -i -o ${DEPLOY_PKG} .