grpc-golang实现账号and密码认证

// I would recommend to use interceptors:

// client
grpc.Dial(target, grpc.WithPerRPCCredentials(&loginCreds{
    Username: "admin",
    Password: "admin123",
}))

type loginCreds struct {
    Username, Password string
}

func (c *loginCreds) GetRequestMetadata(context.Context, ...string) (map[string]string, error) {
    return map[string]string{
        "username": c.Username,
        "password": c.Password,
    }, nil
}

func (c *loginCreds) RequireTransportSecurity() bool {
    return true
}

// server
grpc.NewServer(
    grpc.StreamInterceptor(streamInterceptor),
    grpc.UnaryInterceptor(unaryInterceptor)
)

func streamInterceptor(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
    if err := authorize(stream.Context()); err != nil {
        return err
    }

    return handler(srv, stream)
}

func unaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
    if err := authorize(ctx); err != nil {
        return err
    }

    return handler(ctx, req)
}

func authorize(ctx context.Context) error {
    if md, ok := metadata.FromContext(ctx); ok {
        if len(md["username"]) >  && md["username"][] == "admin" &&
            len(md["password"]) >  && md["password"][] == "admin123" {
            return nil
        }

        return AccessDeniedErr
    }

    return EmptyMetadataErr
}