helloworld: go clarity tweaks and go modules for shell (#1908)

* helloworld: go clarity tweaks and go modules for shell

* helloworld: go and shell README and comment alignment

docs/serving/samples/hello-world/helloworld-go/Dockerfile

@@ -6,8 +6,8 @@ FROM golang:1.13 as builder
 # Create and change to the app directory.
 WORKDIR /app
 
-# Retrieve application dependencies.
-# This allows the container build to reuse cached dependencies.
+# Retrieve application dependencies using go modules.
+# Allows container builds to reuse downloaded dependencies.
 COPY go.* ./
 RUN go mod download
 
@@ -15,6 +15,7 @@ RUN go mod download
 COPY . ./
 
 # Build the binary.
+# -mod=readonly ensures immutable go.mod and go.sum in container builds.
 RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
 # Use the official Alpine image for a lean production container.

docs/serving/samples/hello-world/helloworld-go/README.md

@@ -42,7 +42,7 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    )
 
    func handler(w http.ResponseWriter, r *http.Request) {
-     log.Print("Hello world received a request.")
+     log.Print("helloworld: received a request")
      target := os.Getenv("TARGET")
      if target == "" {
        target = "World"
@@ -51,7 +51,7 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    }
 
    func main() {
-     log.Print("Hello world sample started.")
+     log.Print("helloworld: starting server...")
 
      http.HandleFunc("/", handler)
 
@@ -60,6 +60,7 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
        port = "8080"
      }
 
+     log.Printf("helloworld: listening on port %s", port)
      log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
    }
    ```
@@ -77,8 +78,8 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    # Create and change to the app directory.
    WORKDIR /app
 
-   # Retrieve application dependencies.
-   # This allows the container build to reuse cached dependencies.
+   # Retrieve application dependencies using go modules.
+   # Allows container builds to reuse downloaded dependencies.
    COPY go.* ./
    RUN go mod download
 
@@ -86,6 +87,7 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    COPY . ./
 
    # Build the binary.
+   # -mod=readonly ensures immutable go.mod and go.sum in container builds.
    RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
    # Use the official Alpine image for a lean production container.

docs/serving/samples/hello-world/helloworld-go/helloworld.go

@@ -8,7 +8,7 @@ import (
 )
 
 func handler(w http.ResponseWriter, r *http.Request) {
-	log.Print("Hello world received a request.")
+	log.Print("helloworld: received a request")
 	target := os.Getenv("TARGET")
 	if target == "" {
 		target = "World"
@@ -17,7 +17,7 @@ func handler(w http.ResponseWriter, r *http.Request) {
 }
 
 func main() {
-	log.Print("Hello world sample started.")
+	log.Print("helloworld: starting server...")
 
 	http.HandleFunc("/", handler)
 
@@ -26,5 +26,6 @@ func main() {
 		port = "8080"
 	}
 
+	log.Printf("helloworld: listening on port %s", port)
 	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
 }

docs/serving/samples/hello-world/helloworld-shell/Dockerfile

@@ -1,26 +1,32 @@
-# Use the offical Golang image to create a build artifact.
+# 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:1.13 as builder
+
+# Create and change to the app directory.
+WORKDIR /app
+
+# Retrieve application dependencies using go modules.
+# Allows container builds to reuse downloaded dependencies.
+COPY go.* ./
+RUN go mod download
 
 # Copy local code to the container image.
-WORKDIR /go/src/github.com/knative/docs/helloworld-shell
-COPY invoke.go .
+COPY invoke.go ./
 
-# Build the command inside the container.
-# (You may fetch or manage dependencies here,
-# either manually or with a tool like "godep".)
-RUN CGO_ENABLED=0 GOOS=linux go build -v -o invoke
+# Build the binary.
+# -mod=readonly ensures immutable go.mod and go.sum in container builds.
+RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
-# The official Alpine base image
+# Use the official Alpine image for a lean production container.
 # https://hub.docker.com/_/alpine
-# Use a Docker multi-stage build to create a lean production image.
 # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-FROM alpine:3.10
+FROM alpine:3
+RUN apk add --no-cache ca-certificates
 
-# Copy Go binary
-COPY --from=builder /go/src/github.com/knative/docs/helloworld-shell/invoke /invoke
-COPY script.sh .
+# Copy the binary to the production image from the builder stage.
+COPY --from=builder /app/server /server
+COPY script.sh ./
 
 # Run the web service on container startup.
-CMD ["/invoke"]
+CMD ["/server"]

docs/serving/samples/hello-world/helloworld-shell/README.md

@@ -42,64 +42,75 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-shell
    package main
 
    import (
-      "fmt"
-      "log"
-      "net/http"
-      "os"
-      "os/exec"
+     "fmt"
+     "log"
+     "net/http"
+     "os"
+     "os/exec"
    )
 
    func handler(w http.ResponseWriter, r *http.Request) {
-      cmd := exec.CommandContext(r.Context(), "/bin/sh", "script.sh")
-      cmd.Stderr = os.Stderr
-      out, err := cmd.Output()
-      if err != nil {
-          w.WriteHeader(500)
-      }
-      w.Write(out)
+     log.Print("helloworld: received a request")
+
+     cmd := exec.CommandContext(r.Context(), "/bin/sh", "script.sh")
+     cmd.Stderr = os.Stderr
+     out, err := cmd.Output()
+     if err != nil {
+       w.WriteHeader(500)
+     }
+     w.Write(out)
    }
 
    func main() {
-      http.HandleFunc("/", handler)
+     log.Print("helloworld: starting server...")
 
-      port := os.Getenv("PORT")
-      if port == "" {
-          port = "8080"
-      }
+     http.HandleFunc("/", handler)
 
-      log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
+     port := os.Getenv("PORT")
+     if port == "" {
+       port = "8080"
+     }
+
+     log.Printf("helloworld: listening on %s", port)
+     log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
    }
    ```
 
 1. Create a new file named `Dockerfile` and copy the code block below into it.
 
    ```docker
-   # Use the offical Golang image to create a build artifact.
+   # 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:1.13 as builder
+
+   # Create and change to the app directory.
+   WORKDIR /app
+
+   # Retrieve application dependencies using go modules.
+   # Allows container builds to reuse downloaded dependencies.
+   COPY go.* ./
+   RUN go mod download
 
    # Copy local code to the container image.
-   WORKDIR /go/src/github.com/knative/docs/helloworld-shell
-   COPY invoke.go .
+   COPY invoke.go ./
 
-   # Build the command inside the container.
-   # (You may fetch or manage dependencies here,
-   # either manually or with a tool like "godep".)
-   RUN CGO_ENABLED=0 GOOS=linux go build -v -o invoke
+   # Build the binary.
+   # -mod=readonly ensures immutable go.mod and go.sum in container builds.
+   RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
-   # The official Alpine base image
+   # Use the official Alpine image for a lean production container.
    # https://hub.docker.com/_/alpine
-   # Use a Docker multi-stage build to create a lean production image.
    # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-   FROM alpine:3.10
+   FROM alpine:3
+   RUN apk add --no-cache ca-certificates
 
-   # Copy Go binary
-   COPY --from=builder /go/src/github.com/knative/docs/helloworld-shell/invoke /invoke
-   COPY script.sh .
+   # Copy the binary to the production image from the builder stage.
+   COPY --from=builder /app/server /server
+   COPY script.sh ./
 
    # Run the web service on container startup.
-   CMD ["/invoke"]
+   CMD ["/server"]
    ```
 
 1. Create a new file, `service.yaml` and copy the following service definition
@@ -122,6 +133,13 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-shell
                  value: "Shell Sample v1"
    ```
 
+1. Use the go tool to create a
+   [`go.mod`](https://github.com/golang/go/wiki/Modules#gomod) manifest.
+
+   ```shell
+   go mod init github.com/knative/docs/docs/serving/samples/hello-world/helloworld-shell
+   ```
+
 ## Building and deploying the sample
 
 Once you have recreated the sample code files (or used the files in the sample

docs/serving/samples/hello-world/helloworld-shell/go.mod

@@ -0,0 +1,3 @@
+module github.com/knative/docs/docs/serving/samples/hello-world/helloworld-shell
+
+go 1.13

docs/serving/samples/hello-world/helloworld-shell/invoke.go

@@ -9,6 +9,8 @@ import (
 )
 
 func handler(w http.ResponseWriter, r *http.Request) {
+	log.Print("helloworld: received a request")
+
 	cmd := exec.CommandContext(r.Context(), "/bin/sh", "script.sh")
 	cmd.Stderr = os.Stderr
 	out, err := cmd.Output()
@@ -19,6 +21,8 @@ func handler(w http.ResponseWriter, r *http.Request) {
 }
 
 func main() {
+	log.Print("helloworld: starting server...")
+
 	http.HandleFunc("/", handler)
 
 	port := os.Getenv("PORT")
@@ -26,5 +30,6 @@ func main() {
 		port = "8080"
 	}
 
+	log.Printf("helloworld: listening on %s", port)
 	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
 }

test/sampleapp/config.yaml

@@ -58,6 +58,9 @@ languages:
       - "Dockerfile"
   - language: "shell"
     expectedOutput: "Hello Shell Sample v1!"
+    preCommands:
+      - exec: "cp"
+        args: "../../docs/serving/samples/hello-world/helloworld-shell/go.mod helloworld-shell_tmp/go.mod"
     copies:
       - "script.sh"
       - "invoke.go"