Feature: Faster start & stop times (#648)

* Updates starting and stopping routines to be a bit more parallel with less waiting required

* Removes stop, removes debugging output

* linting and test fixes

* Add extra kill switch for exiting on exchange loading delay

* Fixes fun math

* breaks loop instead of switch. Moves param warns higher

* Removes unceccary gos. passes in cfg to remove data race

* Removes os signal processing. Fixes bad master merge

engine/connection.go

@@ -1,18 +1,18 @@
 package engine
 
 import (
-	"errors"
+	"fmt"
 	"sync/atomic"
 
 	"github.com/thrasher-corp/gocryptotrader/config"
 	"github.com/thrasher-corp/gocryptotrader/connchecker"
+	"github.com/thrasher-corp/gocryptotrader/engine/subsystem"
 	"github.com/thrasher-corp/gocryptotrader/log"
 )
 
 // connectionManager manages the connchecker
 type connectionManager struct {
 	started int32
-	stopped int32
 	conn    *connchecker.Checker
 }
 
@@ -23,8 +23,8 @@ func (c *connectionManager) Started() bool {
 
 // Start starts an instance of the connection manager
 func (c *connectionManager) Start(conf *config.ConnectionMonitorConfig) error {
-	if atomic.AddInt32(&c.started, 1) != 1 {
-		return errors.New("connection manager already started")
+	if !atomic.CompareAndSwapInt32(&c.started, 0, 1) {
+		return fmt.Errorf("connection manager %w", subsystem.ErrSubSystemAlreadyStarted)
 	}
 
 	log.Debugln(log.ConnectionMgr, "Connection manager starting...")
@@ -44,17 +44,14 @@ func (c *connectionManager) Start(conf *config.ConnectionMonitorConfig) error {
 // Stop stops the connection manager
 func (c *connectionManager) Stop() error {
 	if atomic.LoadInt32(&c.started) == 0 {
-		return errors.New("connection manager not started")
-	}
-
-	if atomic.AddInt32(&c.stopped, 1) != 1 {
-		return errors.New("connection manager is already stopped")
+		return fmt.Errorf("connection manager %w", subsystem.ErrSubSystemNotStarted)
 	}
+	defer func() {
+		atomic.CompareAndSwapInt32(&c.started, 1, 0)
+	}()
 
 	log.Debugln(log.ConnectionMgr, "Connection manager shutting down...")
 	c.conn.Shutdown()
-	atomic.CompareAndSwapInt32(&c.stopped, 1, 0)
-	atomic.CompareAndSwapInt32(&c.started, 1, 0)
 	log.Debugln(log.ConnectionMgr, "Connection manager stopped.")
 	return nil
 }