Context should be passed per operation

[christian-roggia]

Following the standard patterns for storage and databases written in Golang, the context should be passed per operation and not per connection.

The current setup works in the following way:

cete.NewGRPCClientWithContext(..., ctx)

and Get / Set / Delete / etc. operation are executed this way:

cli.Set(req)

the expected call is the following:

cli.Set(ctx, req)

and this is useful when we want to limit, for example, how long a Set or Get should takes before timing out:

ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
defer cancel()

cli.Set(ctx, req)

this useful to control timeouts, cascade cancellation, and similar operations.

Also, as a final note, the context variable in Golang is normally expected to be the first parameter of the function, this is not a written rule but a very common and popular standard:

cete.NewGRPCClientWithContext(ctx, ...)

See https://golang.org/src/net/dial.go#L369 as an example.