exchanges: Initial context propagation (#744)

* gct: phase one context awareness pass

* exchanges: context propagation pass

* common/requester: force context requirement

* gctcli/exchanges: linter fix

* rpcserver: fix test using dummy rpc server

* backtester: fix comments

* grpc: add correct cancel and timeout for commands

* rpcserver_test: add comment on dummy server

* common: deprecated SendHTTPGetRequest

* linter: fix

* linter: turn on no context check

* apichecker: fix context linter issue

* binance: use param context

* common: remove checks as this gets executed before main

* common: change mutex to RW as clients can be used by multiple go routines.

* common: remove init and JIT default client. Unexport global variables and add protection.

* common: Add comments

* bithumb: after dinner mints fix

exchanges/request/request.go

@@ -28,6 +28,7 @@ var (
 	errInvalidPath            = errors.New("invalid path")
 	errHeaderResponseMapIsNil = errors.New("header response map is nil")
 	errFailedToRetryRequest   = errors.New("failed to retry request")
+	errContextRequired        = errors.New("context is required")
 )
 
 // New returns a new Requester
@@ -54,6 +55,10 @@ func (r *Requester) SendPayload(ctx context.Context, ep EndpointLimit, newReques
 		return errRequestSystemIsNil
 	}
 
+	if ctx == nil {
+		return errContextRequired
+	}
+
 	defer r.timedLock.UnlockIfLocked()
 
 	if newRequest == nil {