Add parameter to define timeout for Modbus RTU operations

[tobima]

I run into the issue mentioned in pull request #258 with an ORNO 3 phase meter. These changes add a command line parameter -t timeout to change to default timeout for Modbus RTU operations.

fix https://github.com/volkszaehler/mbmd/issues/266

[andig]

Thank you for the PR. Could you please make the timeout a time.Duration instead of an int?

[tobima]

Thank you for the PR. Could you please make the timeout a time.Duration instead of an int?

Good idea. I already commited these change.

[andig]

Thought about this some more:

• should probably do this for RTU and TCP both
• PR breaks public API. One option of avoiding that would be adding ...Option als variadic parameter. Or (probably preferred) NewRTU already has a Timeout function- why not call that after creating the connection?

[tobima]

Good catch. I didn't realize that there was already a Timeout function for RTU and TCP. It should look better now.

[tobima]

I realized that the shorthand parameter -t conflits with the -t, --type string Register type to write: holding|coil (default "holding") of the mbmd write command. Should the shorthand paramter be removed for the timeout parameter as the other one already exists or could the shorthand parameter for the write command be renamed or removed as this is only an experimental feature at the moment?

[andig]

Thank you, nice PR!

[isarrider]

maybe related to #277

[isarrider]

we should note here, that it is not only RTU, but TCP too! also we should update the https://github.com/volkszaehler/mbmd/blob/master/mbmd.dist.yaml