Add RPC Timout request and prevent blocking while waiting response

[yogihardi]

closes #108

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this PR is related to this request #98

The most significant issue was the rpc.Handler.Request function, in which the go routine could block indefinitely waiting for a response from the server.

I found that there are missed fixes from the last PR on the following line
https://github.com/eclipse/paho.golang/blob/e818d6af9263c1ff1c68749d9e87defb8f51690f/paho/extensions/rpc/rpc.go#L76

also, I proposed request timeout on RPC Request

[MattBrittan]

Thanks for your PR - I have added a few comments. Please note that you will need to complete the CLA (see contributingh.md) before this can be accepted (this process ensures that we have verification that all contributions are correctly licensed).

[yogihardi]

hi @MattBrittan ,

thank you for your review.
i couldn't verify my eca, even though my email address is same and correct.

I got the following error message:

Failures:
Anonymous (<my email account>@****.com)

[MattBrittan]

thank you for your review. i couldn't verify my eca, even though my email address is same and correct.

I have manually checked and the ECA system does not appear to have your address on file (note that email addresses used in Github are publicly available and easily retrieved from the patch). Can you please confirm that you have created an account and signed the ECA?

I'm OK with the PR itself (but unfortunately cannot accept it until we get the ECA sorted). Personally I'd probably just return the errCtx because most users would expect to check for the standard context errors but can also see some advantages to your approach.