Build all micro/examples for release-X.X.X branches (#1683)

* Build all the examples on push to any release branch

.github/workflows/micro-examples.yml

@@ -0,0 +1,34 @@
+name: Build all github.com/micro/examples
+on:
+  push: 
+    branches:
+      - 'release-**'
+
+jobs:
+
+  build:
+    name: Build repos
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go 1.13
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.13
+      id: go
+
+    - name: Check out this code
+      uses: actions/checkout@v2
+      with:
+        path: 'go-micro'
+
+    - name: Check out code examples
+      uses: actions/checkout@v2
+      with:
+        repository: 'micro/examples'
+        path: 'examples'
+
+    - name: Build all
+      run: $GITHUB_WORKSPACE/go-micro/.github/workflows/scripts/build-all-examples.sh $GITHUB_SHA
+      working-directory: examples
+    

.github/workflows/scripts/build-all-examples.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+# set -x
+
+function build_binary {
+    echo building $1
+    pushd $1
+    go build
+    local ret=$?
+    if [ $ret -gt 0 ]; then 
+        failed=1
+        failed_arr+=($1)
+    fi
+    popd
+}
+
+function is_main {
+    grep "package main" -l -dskip $1/*.go > /dev/null 2>&1
+}
+
+
+function check_dir {
+    is_main $1
+    local ret=$?
+    if [ $ret == 0 ]; then
+        build_binary $1 $2
+    fi
+    for filename in $1/*; do
+        if [ -d $filename ]; then
+            check_dir $filename $2
+        fi
+    done
+}
+failed_arr=()
+failed=0
+this_hash=$1
+go mod init github.com/micro/examples
+go mod edit -require=github.com/micro/go-micro/v2@$1 
+check_dir . $1
+if [ $failed -gt 0 ]; then
+    echo Some builds failed
+    printf '%s\n' "${failed_arr[@]}"
+fi
+exit $failed