Feat/customize rpc timeout

[bruce1125]

update docs to explain how to customize the timeout value

[coveralls]

Pull Request Test Coverage Report for Build 8812929899

Details

• 10 of 10 (100.0%) changed or added relevant lines in 1 file are covered.
• 11 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.04%) to 62.129%

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Files with Coverage Reduction	New Missed Lines	%
groups/memory_group_service.go	1	84.25%
cluster/nats_rpc_client.go	10	84.81%
<!--	Total:	11		-->

Totals
Change from base Build 8807700949:	0.04%
Covered Lines:	4833
Relevant Lines:	7779

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💛 - Coveralls

[felipejfc]

FYI new version released with this change: https://github.com/topfreegames/pitaya/releases/tag/v2.11.0

[bruce1125]

LGTM. We should create a helper later like, a new method in the interface like: RPC(msg, route, ..., timeout) which sets this value on the context, so that this feature would be easier accessible and we avoid unmarshal errors on the timeout value

That's a good idear, waiting for the new API.