cmd/go/internal/modfetch: add missing error checks

src/cmd/go/internal/modfetch/coderepo.go

@@ -541,6 +541,9 @@ func (r *codeRepo) Zip(dst io.Writer, version string) error {
 			return err
 		}
 		w, err := zw.Create(r.modPrefix(version) + "/" + name)
+		if err != nil {
+			return err
+		}
 		lr := &io.LimitedReader{R: rc, N: size + 1}
 		if _, err := io.Copy(w, lr); err != nil {
 			return err

src/cmd/go/internal/modfetch/pseudo.go

@@ -98,6 +98,9 @@ func IsPseudoVersion(v string) bool {
 // embedded in the pseudo-version is not a valid time.
 func PseudoVersionTime(v string) (time.Time, error) {
 	timestamp, _, err := parsePseudoVersion(v)
+	if err != nil {
+		return time.Time{}, err
+	}
 	t, err := time.Parse("20060102150405", timestamp)
 	if err != nil {
 		return time.Time{}, fmt.Errorf("pseudo-version with malformed time %s: %q", timestamp, v)

src/cmd/go/internal/modfetch/pseudo_test.go

@@ -60,6 +60,13 @@ func TestPseudoVersionTime(t *testing.T) {
 	}
 }
 
+func TestInvalidPseudoVersionTime(t *testing.T) {
+	const v = "---"
+	if _, err := PseudoVersionTime(v); err == nil {
+		t.Error("expected error, got nil instead")
+	}
+}
+
 func TestPseudoVersionRev(t *testing.T) {
 	for _, tt := range pseudoTests {
 		rev, err := PseudoVersionRev(tt.version)