gogio: read -signpass from environment variable if it isn't provided as an argument

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gogio/build_info.go

@@ -56,6 +56,10 @@ func newBuildInfo(pkgPath string) (*buildInfo, error) {
 	if err != nil {
 		return nil, err
 	}
+	sp := *signPass
+	if sp == "" {
+		sp = os.Getenv("GOGIO_SIGNPASS")
+	}
 	bi := &buildInfo{
 		appID:          appID,
 		archs:          getArchs(),
@@ -70,7 +74,7 @@ func newBuildInfo(pkgPath string) (*buildInfo, error) {
 		target:         *target,
 		version:        ver,
 		key:            *signKey,
-		password:       *signPass,
+		password:       sp,
 		notaryAppleID:  *notaryID,
 		notaryPassword: *notaryPass,
 		notaryTeamID:   *notaryTeamID,

gogio/help.go

@@ -72,6 +72,7 @@ The -signkey flag specifies the path of the keystore, used for signing Android a
 or specifies the name of key on Keychain to sign MacOS app.
 
 The -signpass flag specifies the password of the keystore, ignored if -signkey is not provided.
+If -signpass is not sepecified it will be read from the environment variable GOGIO_SIGNPASS.
 
 The -notaryid flag specifies the Apple ID to use for notarization of MacOS app.