设置为上海时区正确示范，需要转义斜杠为%2f

DSN: "username:password@tcp(localhost:3306)/tablename?charset=utf8mb4&parseTime=True&loc=Asia%2fShanghai"

正常的本地时区情况

DSN: "username:password@tcp(localhost:3306)/tablename?charset=utf8mb4&parseTime=True&loc=Local"

错误的

DSN: "username:password@tcp(localhost:3306)/tablename?loc=Asia/Shanghai"