Prevent multiple request to be made to the same device before a respo…

…nse is returned

client.go

@@ -1,11 +1,14 @@
 package canopen
 
 import (
-	"time"
-
 	"github.com/FabianPetersen/can"
+	"github.com/jpillora/maplock"
+	"strconv"
+	"time"
 )
 
+var m = maplock.New()
+
 // A Client handles message communication by sending a request
 // and waiting for the response.
 type Client struct {
@@ -16,6 +19,11 @@ type Client struct {
 // Do sends a request and waits for a response.
 // If the response frame doesn't arrive on time, an error is returned.
 func (c *Client) Do(req *Request) (*Response, error) {
+	// Do not allow multiple messages for the same device
+	key := strconv.Itoa(int(req.ResponseID))
+	m.Lock(key)
+	defer m.Unlock(key)
+
 	rch := can.Wait(c.Bus, req.ResponseID, c.Timeout)
 
 	if err := c.Bus.Publish(req.Frame.CANFrame()); err != nil {

go.mod

@@ -2,4 +2,7 @@ module github.com/FabianPetersen/canopen
 
 go 1.15
 
-require github.com/FabianPetersen/can v0.0.3
+require (
+	github.com/FabianPetersen/can v0.0.3
+	github.com/jpillora/maplock v0.0.0-20160420012925-5c725ac6e22a
+)

go.sum

@@ -1,8 +1,6 @@
 github.com/FabianPetersen/can v0.0.3 h1:AvNdtYRx/Qqd9ecVmPPk4/U27GT5kyvurtriWyASoMU=
 github.com/FabianPetersen/can v0.0.3/go.mod h1:K+0T7NSTiAhcH/zIYFPj4o256RKIwQ1Y/uHTC9MyK4I=
-github.com/brutella/can v0.0.1 h1:Rz+2Zuje3NT79daon8wPN9+VphH3/kl1DP8Dhf/k1NI=
-github.com/brutella/can v0.0.1/go.mod h1:NYDxbQito3w4+4DcjWs/fpQ3xyaFdpXw/KYqtZFU98k=
-golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06 h1:0oC8rFnE+74kEmuHZ46F6KHsMr5Gx2gUQPuNz28iQZM=
-golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+github.com/jpillora/maplock v0.0.0-20160420012925-5c725ac6e22a h1:40K0UjFKjfaXcJaGMgf9C0fOzwDxPZMOI0CPbNP89cQ=
+github.com/jpillora/maplock v0.0.0-20160420012925-5c725ac6e22a/go.mod h1:bn3xq9G+QDq2j6fczyaTq47L6980t7/NnqCnCK7kqD0=
 golang.org/x/sys v0.0.0-20190429190828-d89cdac9e872 h1:cGjJzUd8RgBw428LXP65YXni0aiGNA4Bl+ls8SmLOm8=
 golang.org/x/sys v0.0.0-20190429190828-d89cdac9e872/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=