simplify context and move set offset to context commit

[db7]

No description provided.

[heltonmarx]

You're increase this variable here, but probably is reading in other coprocess. For this case, it's necessary protect it with mutex.

[db7]

Actually, it cannot/should not be accessed concurrently.

• counters.stores can only be incremented by the goroutine that creates the context, which is the partition-goroutine.
• promise-goroutines (coming from emit confirmations) or the partition-goroutine may read stores if they call ctx.commit()
• but only one of them will call it (the last one calling tryCommit()) and that happens after at least one lock-protected critical section, which will act as a memory barrier anyways.

The comment made me realize though, that counters.calls doesn't need a lock too. So I removed that lock and also renamed the counters.

[heltonmarx]

This mutex can be substituted by a RWMutex, considering that you're need create a method like:

func (ctx *context) Stores() int {
	ctx.m.RLock()
	defer ctx.m.RUnlock()
	return ctx.counters.stores
}