Add error handling to fmt.Fprintln()

kadai3-1/lfcd85/typinggame/typinggame.go

@@ -8,6 +8,8 @@ import (
 	"math/rand"
 	"os"
 	"time"
+
+	"github.com/hashicorp/go-multierror"
 )
 
 // Words stores a slice of words which is used for the game.
@@ -21,38 +23,42 @@ type Game struct {
 
 // Execute starts the game using standard input and output.
 func Execute(g Game) error {
-	g.run(inputChannel(os.Stdin), os.Stdout)
-	return nil
+	err := g.run(inputChannel(os.Stdin), os.Stdout)
+	return err
 }
 
-func (g *Game) run(ch <-chan string, w io.Writer) {
+func (g *Game) run(ch <-chan string, w io.Writer) error {
+	var result error
+
 	bc := context.Background()
 	ctx, cancel := context.WithTimeout(bc, g.TimeLimit)
 	defer cancel()
 
-	fmt.Fprintln(w, "Let's type the standard package names! ( Time limit:", g.TimeLimit, ")")
+	result = printWithMultiErr(w, result, "Let's type the standard package names! ( Time limit:", g.TimeLimit, ")")
 
 	var score int
 	rand.Seed(time.Now().UnixNano())
 	word := g.Words[rand.Intn(len(g.Words))]
 LOOP:
 	for {
-		fmt.Fprintln(w, ">", word)
+		result = printWithMultiErr(w, result, ">", word)
 		select {
 		case input := <-ch:
 			if input == word {
 				score++
-				fmt.Fprintln(w, input, "... OK! current score:", score)
+				result = printWithMultiErr(w, result, input, "... OK! current score:", score)
 				word = g.Words[rand.Intn(len(g.Words))]
 			} else {
-				fmt.Fprintln(w, input, "... NG: try again.")
+				result = printWithMultiErr(w, result, input, "... NG: try again.")
 			}
 		case <-ctx.Done():
-			fmt.Fprintln(w)
-			fmt.Fprintln(w, g.TimeLimit, "has passed: you correctly typed", score, "package(s)!")
+			result = printWithMultiErr(w, result)
+			result = printWithMultiErr(w, result, g.TimeLimit, "has passed: you correctly typed", score, "package(s)!")
 			break LOOP
 		}
 	}
+
+	return result
 }
 
 func inputChannel(r io.Reader) <-chan string {
@@ -66,3 +72,10 @@ func inputChannel(r io.Reader) <-chan string {
 	}()
 	return ch
 }
+
+func printWithMultiErr(w io.Writer, result error, a ...interface{}) error {
+	if _, err := fmt.Fprintln(w, a...); err != nil {
+		result = multierror.Append(result, err)
+	}
+	return result
+}