Fix compile error on Darwin platforms

[maryis]

This is a fix to desolve build failure on macOS target due to duplicate getSendQueueLen definition after adding sockio_bsd.go

Description

After adding sockio_bsd.go, builds targeting macOS (darwin) fail with a duplicate symbol error:

sockio_darwin.go:28:6: getSendQueueLen redeclared in this block

Root Cause

sockio_bsd.go includes the following build constraint:

//go:build aix || darwin || dragonfly || freebsd || netbsd || openbsd || solaris
// +build aix darwin dragonfly freebsd netbsd openbsd solaris
Because darwin is included in this build tag, sockio_bsd.go is compiled when GOOS=darwin.

At the same time, sockio_darwin.go is also compiled (due to the _darwin.go filename suffix).

Both files define:

func getSendQueueLen(...)

As a result, when building for macOS (including cross-compilation, e.g. arm64 Big Sur bottles), both files are included in the same package, causing a redeclaration error.

Reproduction

Build the package with:

GOOS=darwin GOARCH=arm64 go build ./...

Expected Behavior

Only one platform-specific implementation of getSendQueueLen should be compiled per target OS.

Suggested Fix

If sockio_bsd.go is not intended to apply to macOS, remove darwin from its build constraint:

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[maryis]

closed