Implement #FF0

app/main.go

 import (
 	"bufio"
 	"fmt"
+	"io"
 	"os"
 )
 
-// Ensures gofmt doesn't remove the "fmt" import in stage 1 (feel free to remove this!)
-var _ = fmt.Print
+type Context struct {
+	stdout io.Writer
+	stderr io.Writer
+	stdin  io.Reader
+}
 
-func main() {
+type GetCommandResult int
+
+const (
+	GetCommandResultOk GetCommandResult = iota
+	GetCommandResultError
+)
+
+func getCommand(ctx *Context) (string, error) {
 	fmt.Print("$ ")
-	command, err := bufio.NewReader(os.Stdin).ReadString('\n')
+	command_line, err := bufio.NewReader(ctx.stdin).ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	command, err := parseCommand(ctx, command_line)
 	if err != nil {
-		fmt.Fprintln(os.Stderr, "Error reading input: ", err)
-		os.Exit(1)
+		return "", err
+	}
+	return command, nil
+}
+
+func parseCommand(ctx *Context, command_line string) (string, error) {
+	_ = ctx
+	return command_line[:len(command_line)-1], nil
+}
+
+func handleCommand(ctx Context, command string) {
+	fmt.Fprintln(ctx.stderr, command+": command not found")
+}
+
+func main() {
+	ctx := Context{
+		stdout: os.Stdout,
+		stderr: os.Stderr,
+		stdin:  os.Stdin,
+	}
+	for {
+		command, err := getCommand(&ctx)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "Error reading input: ", err)
+			os.Exit(1)
+		}
+		handleCommand(ctx, command)
 	}
-	fmt.Println(command[:len(command)-1] + ": command not found")
 }