go/src/cmd/go/internal/base/limit.go

var NetLimitGodebug …

// NetLimit returns the limit on concurrent network operations
// configured by GODEBUG=cmdgonetlimit, if any.
//
// A limit of 0 (indicated by 0, true) means that network operations should not
// be allowed.
func NetLimit() (int, bool) { … }

// AcquireNet acquires a semaphore token for a network operation.
func AcquireNet() (release func(), err error) { … }

var netLimitOnce …

var netLimitSem …

type netTokenChecker …

func (c *netTokenChecker) panicUnreleased() { … }