您最有可能使用flag.FlagSet了flag程序包的默认标志集（）。请注意，您可能不是唯一使用它的人。如果导入其他软件包，它们也可能会注册标志，这些标志将像您自己的标志（已注册的标志）一样进行处理。

看这个简单的例子：

import (
    "flag"
    _ "testing"
)

func main() {
    flag.Int("port", 80, "port to use")
    flag.Parse()
}

这个程序注册一个port标志，别无其他。但是它也导入了testing注册很多标志的包。

使用-h命令行参数运行它，输出为：

  -port int
        port to use (default 80)
  -test.bench string
        regular expression per path component to select benchmarks to run
  -test.benchmem
        print memory allocations for benchmarks
  -test.benchtime duration
        approximate run time for each benchmark (default 1s)
  -test.blockprofile string
        write a goroutine blocking profile to the named file after execution
  -test.blockprofilerate int
        if >= 0, calls runtime.SetBlockProfileRate() (default 1)
  -test.count n
        run tests and benchmarks n times (default 1)
  -test.coverprofile string
        write a coverage profile to the named file after execution
  -test.cpu string
        comma-separated list of number of CPUs to use for each test
  -test.cpuprofile string
        write a cpu profile to the named file during execution
  -test.memprofile string
        write a memory profile to the named file after execution
  -test.memprofilerate int
        if >=0, sets runtime.MemProfileRate
  -test.outputdir string
        directory in which to write profiles
  -test.parallel int
        maximum test parallelism (default 4)
  -test.run string
        regular expression to select tests and examples to run
  -test.short
        run smaller test suite to save time
  -test.timeout duration
        if positive, sets an aggregate time limit for all tests
  -test.trace string
        write an execution trace to the named file after execution
  -test.v
        verbose: print additional output
exit status 2

如果您不希望将自己的标志与其他程序包的标志混合使用，请flag.FlagSet通过调用来创建和使用自己的标志flag.NewFlagSet()，但是当然您必须使用其方法而不是flag程序包的顶级功能。