Fix race condition and enable race diagnostics

.goreleaser.yml

@@ -10,7 +10,7 @@ builds:
 - id: evcc
   main: main.go
   flags:
-  - -tags=release
+  - -race -tags=release
   ldflags:
   - -X github.com/evcc-io/evcc/server.Version={{.Version}} -X github.com/evcc-io/evcc/server.Commit={{.ShortCommit}} -s -w
   env:
@@ -105,4 +105,4 @@ brews:
         <key>StandardErrorPath</key>
         <string>#{var}/log/evcc.log</string>
       </dict>
-    </plist>
+    </plist>

Makefile

@@ -56,7 +56,7 @@ test:
 
 build:
 	@echo Version: $(VERSION) $(BUILD_DATE)
-	go build -v $(BUILD_TAGS) $(BUILD_ARGS)
+	go build -race -v $(BUILD_TAGS) $(BUILD_ARGS)
 
 release-test:
 	goreleaser --snapshot --skip-publish --rm-dist

core/loadpoint.go

@@ -1281,7 +1281,10 @@ func (lp *LoadPoint) updateChargePower() {
 			return err
 		}
 
+		lp.Lock()
 		lp.chargePower = value // update value if no error
+		lp.Unlock()
+
 		lp.log.DEBUG.Printf("charge power: %.0fW", value)
 		lp.publish("chargePower", value)