Add option to define coroutineContext for coroutine functions

[markGilchrist]

this will prevent networkonmainthread exception

[codecov]

Codecov Report

Merging #387 into master will decrease coverage by 0.19%.
The diff coverage is 40%.

@@             Coverage Diff             @@
##             master     #387     +/-   ##
===========================================
- Coverage     76.45%   76.25%   -0.2%     
  Complexity      193      193             
===========================================
  Files            33       33             
  Lines           930      935      +5     
  Branches        161      164      +3     
===========================================
+ Hits            711      713      +2     
  Misses          134      134             
- Partials         85       88      +3

Impacted Files	Coverage Δ	Complexity Δ
...com/github/kittinunf/fuel/coroutines/Coroutines.kt	40.74% <40%> (-0.17%)	0 <0> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 52849fe...9f893d4. Read the comment docs.

[avaitla]

Was the CommonPool context in the coroutines code there before and accidentally removed or is there some other reason it needs to be here for the caller to only invoke launch(UI)? Not too familiar with coroutines, and am curious to know why it worked before.

[kittinunf]

I think this is reasonable to merge. Do you think we should add test for checking on the execution thread as well? So that we could have tests that cover us in the future.

[markGilchrist]

@kittinunf I have had a look at writing a test for the execution thread and I have run into a bit of a dead end. if you perform a test inside runBlocking the that forces the scope to be run on the blocking thread.

If anyone has any wise ideas they would be very gratefully received

[kittinunf]

I haven't had any good idea either ... let's merge it.