serving/samples: fix up README

Author: grayside

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

@@ -3,12 +3,19 @@
 # https://hub.docker.com/_/golang
 FROM golang:1.13 as builder
 
-# Copy local code to the container image.
+# Create and change to the app directory.
 WORKDIR /app
+
+# Retrieve application dependencies.
+# This allows the container build to reuse cached dependencies.
+COPY go.* ./
+RUN go mod download
+
+# Copy local code to the container image.
 COPY . ./
 
 # Build the binary.
-RUN CGO_ENABLED=0 GOOS=linux go build -v -o helloworld-server
+RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
 # Use the official Alpine image for a lean production container.
 # https://hub.docker.com/_/alpine
@@ -17,7 +24,7 @@ FROM alpine:3
 RUN apk add --no-cache ca-certificates
 
 # Copy the binary to the production image from the builder stage.
-COPY --from=builder /app/helloworld-server /helloworld-server
+COPY --from=builder /app/server /server
 
 # Run the web service on container startup.
-CMD ["/helloworld-server"]
+CMD ["/server"]

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

@@ -74,12 +74,19 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    # https://hub.docker.com/_/golang
    FROM golang:1.13 as builder
 
-   # Copy local code to the container image.
+   # Create and change to the app directory.
    WORKDIR /app
+
+   # Retrieve application dependencies.
+   # This allows the container build to reuse cached dependencies.
+   COPY go.* ./
+   RUN go mod download
+
+   # Copy local code to the container image.
    COPY . ./
 
    # Build the binary.
-   RUN CGO_ENABLED=0 GOOS=linux go build -v -o helloworld-server
+   RUN CGO_ENABLED=0 GOOS=linux go build -mod=readonly -v -o server
 
    # Use the official Alpine image for a lean production container.
    # https://hub.docker.com/_/alpine
@@ -88,10 +95,10 @@ cd knative-docs/docs/serving/samples/hello-world/helloworld-go
    RUN apk add --no-cache ca-certificates
 
    # Copy the binary to the production image from the builder stage.
-   COPY --from=builder /app/helloworld-server /helloworld-server
+   COPY --from=builder /app/server /server
 
    # Run the web service on container startup.
-   CMD ["/helloworld-server"]
+   CMD ["/server"]
    ```
 
 1. Create a new file, `service.yaml` and copy the following service definition