darwin: make Adapter.Connect thread-safe

This change allows multiple concurrent goroutines to call
`Adapter.Connect` without racing.

Fixes #57

adapter_darwin.go

@@ -2,6 +2,7 @@ package bluetooth
 
 import (
 	"errors"
+	"sync"
 	"time"
 
 	"github.com/JuulLabs-OSS/cbgo"
@@ -9,6 +10,8 @@ import (
 
 // Adapter is a connection to BLE devices.
 type Adapter struct {
+	sync.Mutex
+
 	cmd *centralManagerDelegate
 	pmd *peripheralManagerDelegate
 
@@ -18,7 +21,7 @@ type Adapter struct {
 	peripheralFoundHandler func(*Adapter, ScanResult)
 	scanChan               chan error
 	poweredChan            chan error
-	connectChan            chan cbgo.Peripheral
+	connectChan            map[string](chan cbgo.Peripheral)
 
 	connectHandler func(device Addresser, connected bool)
 }
@@ -29,7 +32,8 @@ type Adapter struct {
 var DefaultAdapter = &Adapter{
 	cm:          cbgo.NewCentralManager(nil),
 	pm:          cbgo.NewPeripheralManager(nil),
-	connectChan: make(chan cbgo.Peripheral),
+	connectChan: make(map[string]chan cbgo.Peripheral),
+
 	connectHandler: func(device Addresser, connected bool) {
 		return
 	},
@@ -97,8 +101,14 @@ func (cmd *centralManagerDelegate) DidDiscoverPeripheral(cmgr cbgo.CentralManage
 
 // DidConnectPeripheral when peripheral is connected.
 func (cmd *centralManagerDelegate) DidConnectPeripheral(cmgr cbgo.CentralManager, prph cbgo.Peripheral) {
-	// Unblock now that we're connected.
-	cmd.a.connectChan <- prph
+	cmd.a.Lock()
+	defer cmd.a.Unlock()
+
+	// Ignore this peripheral if we don't have a chan set up for it.
+	if ch, ok := cmd.a.connectChan[prph.Identifier().String()]; ok {
+		// Unblock now that we're connected.
+		ch <- prph
+	}
 }
 
 // makeScanResult creates a ScanResult when peripheral is found.

gap_darwin.go

@@ -105,11 +105,25 @@ func (a *Adapter) Connect(address Addresser, params ConnectionParams) (*Device,
 	if len(prphs) == 0 {
 		return nil, fmt.Errorf("Connect failed: no peer with address: %s", adr.UUID.String())
 	}
+
+	prphCh := make(chan cbgo.Peripheral)
+	id := prphs[0].Identifier().String()
+
+	a.Lock()
+	a.connectChan[id] = prphCh
+	a.Unlock()
+
+	defer func() {
+		a.Lock()
+		defer a.Unlock()
+		delete(a.connectChan, id)
+	}()
+
 	a.cm.Connect(prphs[0], nil)
 
 	// wait on channel for connect
 	select {
-	case p := <-a.connectChan:
+	case p := <-prphCh:
 		d := &Device{
 			cm:           a.cm,
 			prph:         p,