clarify usage

README.md

@@ -15,17 +15,26 @@ Goals:
 
 # How it works
 
-You define the fallback variables in your `main.go`:
+1. You define the fallback version and version printing in `main.go`:
 
 ```
+package main
+
 var (
 	GitRev       = "0000000"
 	GitVersion   = "v0.0.0-pre0+0000000"
 	GitTimestamp = "0000-00-00T00:00:00+0000"
 )
+
+func main() {
+	if (len(os.Args) > 1 && "version" === os.Args[1]) {
+		fmt.Println("My version is", GitVersion, "created at", GitTimestamp)
+	}
+	// ...
+}
 ```
 
-You `go generate` or `go run git.rootprojects.org/root/go-gitver` to generate `xversion.go`:
+2. You `go generate` or `go run git.rootprojects.org/root/go-gitver` to generate `xversion.go`:
 
 ```
 package main
@@ -46,6 +55,17 @@ go run git.rootprojects.org/root/go-gitver
 cat xversion.go
 ```
 
+```go
+// Code generated by go generate; DO NOT EDIT.
+package main
+
+func init() {
+	GitRev = "6dace8255b52e123297a44629bc32c015add310a"
+	GitVersion = "v1.1.4-pre2+g6dace82"
+	GitTimestamp = "2020-07-16T20:48:15-06:00"
+}
+```
+
 <small>**Note**: The file is named `xversion.go` by default so that the
 generated file's `init()` will come later, and thus take priority, over
 most other files.</small>
@@ -56,6 +76,12 @@ See `go-gitver`s self-generated version:
 go run git.rootprojects.org/root/go-gitver version
 ```
 
+```txt
+6dace8255b52e123297a44629bc32c015add310a
+v1.1.4-pre2+g6dace82
+2020-07-16T20:48:15-06:00
+```
+
 # QuickStart
 
 Add this to the top of your main file, so that it runs with `go generate`: