fix serving samples application cannot build docker image (#3532)

* fix serving samples cannot build docker image

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix secrets-go documentation

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix build fail

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix build fail

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix secrets-go documentation

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix secrets-go docs

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix secrets-go docs

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* gix secrets-go docs

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

* fix secrets-go docs

Signed-off-by: zufardhiyaulhaq <zufardhiyaulhaq@gmail.com>

docs/serving/samples/gitwebhook-go/Dockerfile

@@ -12,21 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM golang AS builder
+FROM golang:1.15 as builder
 
 # copy the source
 ADD .   /go/src/github.com/knative/docs/docs/serving/samples/gitwebhook-go
 WORKDIR /go/src/github.com/knative/docs/docs/serving/samples/gitwebhook-go
 
-# install dependencies
+# Ensure Go modules are on and create the go.mod and go.sum files.
-RUN go get github.com/google/go-github/github
+# Also builds the binary
-RUN go get golang.org/x/oauth2
-RUN go get gopkg.in/go-playground/webhooks.v3
-RUN go get gopkg.in/go-playground/webhooks.v3/github
-
-# build the sample
 RUN CGO_ENABLED=0 go build -o /go/bin/webhook-sample .
 
+# Use a Docker multi-stage build to create a lean production image.
 FROM golang:alpine
 
 EXPOSE 8080

docs/serving/samples/gitwebhook-go/go.mod

@@ -0,0 +1,10 @@
+module github.com/knative/docs/docs/serving/samples/gitwebhook-go
+
+go 1.15
+
+require (
+	github.com/google/go-github v17.0.0+incompatible
+	github.com/google/go-querystring v1.1.0 // indirect
+	golang.org/x/oauth2 v0.0.0-20210427180440-81ed05c6b58c
+	gopkg.in/go-playground/webhooks.v3 v3.13.0
+)

docs/serving/samples/grpc-ping-go/Dockerfile

@@ -15,10 +15,7 @@
 # Use the official Golang image to create a build artifact.
 # This is based on Debian and sets the GOPATH to /go.
 # https://hub.docker.com/_/golang
-FROM golang:1.12 as builder
+FROM golang:1.15 as builder
-
-# Retrieve the dependencies.
-RUN go get google.golang.org/grpc
 
 # Copy local code to the container image.
 WORKDIR /go/src/github.com/knative/docs/docs/serving/samples/grpc-ping-go

docs/serving/samples/grpc-ping-go/client/client.go

@@ -1,5 +1,3 @@
-// +build grpcping
-
 package main
 
 import (

docs/serving/samples/grpc-ping-go/go.mod

@@ -0,0 +1,9 @@
+module github.com/knative/docs/docs/serving/samples/grpc-ping-go
+
+go 1.15
+
+require (
+	github.com/golang/protobuf v1.5.2
+	golang.org/x/net v0.0.0-20210505024714-0287a6fb4125
+	google.golang.org/grpc v1.37.0
+)

docs/serving/samples/grpc-ping-go/grpc-ping.go

@@ -1,5 +1,3 @@
-// +build grpcping
-
 package main
 
 import (

docs/serving/samples/grpc-ping-go/proto/ping.pb.go

@@ -1,8 +1,6 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // source: ping.proto
 
-// +build grpcping
-
 package ping
 
 import (

docs/serving/samples/secrets-go/Dockerfile

@@ -1,7 +1,7 @@
 # Use the official Golang image to create a build artifact.
 # This is based on Debian and sets the GOPATH to /go.
 # https://hub.docker.com/_/golang
-FROM golang as builder
+FROM golang:1.15 as builder
 
 # Copy local code to the container image.
 WORKDIR /go/src/github.com/knative/docs/hellosecrets

docs/serving/samples/secrets-go/go.mod

@@ -0,0 +1,5 @@
+module github.com/knative/docs/docs/serving/samples/secrets-go
+
+go 1.15
+
+require cloud.google.com/go/storage v1.15.0

docs/serving/samples/secrets-go/index.md

@@ -91,6 +91,16 @@ cd knative-docs/docs/serving/samples/secrets-go
    }
    ```
 
+1. Create a new file named `go.mod` and paste the following code. This code is Golang module that
+   specifies a module name, dependencies, and the minimal versions.
+   ```go
+   module github.com/knative/docs/docs/serving/samples/secrets-go
+
+   go 1.15
+
+   require cloud.google.com/go/storage v1.15.0
+   ```
+
 1. In your project directory, create a file named `Dockerfile` and copy the code
    block below into it. For detailed instructions on dockerizing a Go app, see
    [Deploying Go servers with Docker](https://blog.golang.org/docker).
@@ -99,7 +109,7 @@ cd knative-docs/docs/serving/samples/secrets-go
    # Use the official Golang image to create a build artifact.
    # This is based on Debian and sets the GOPATH to /go.
    # https://hub.docker.com/_/golang
-   FROM golang as builder
+   FROM golang:1.15 as builder
 
    # Copy local code to the container image.
    WORKDIR /go/src/github.com/knative/docs/hellosecrets