Best way to implement global counters for highly concurrent applications?

If you're trying to synchronize a pool of workers (e.g. allow n goroutines to crunch away at some amount of work) then channels are a very good way to go about it, but if all you actually need is a counter (e.g page views) then they are overkill. The sync and sync/atomic packages are there to help.

import "sync/atomic"

type count32 int32

func (c *count32) inc() int32 {
    return atomic.AddInt32((*int32)(c), 1)
}

func (c *count32) get() int32 {
    return atomic.LoadInt32((*int32)(c))
}

Go Playground Example

Don't use sync/atomic - from the linked page

Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms. These functions require great care to be used correctly. Except for special, low-level applications, synchronization is better done with channels or the facilities of the sync package

Last time I had to do this I benchmarked something which looked like your second example with a mutex and something which looked like your third example with a channel. The channels code won when things got really busy, but make sure you make the channel buffer big.