Fix: fixed race condition in dashboard websocket access

go.sum

+github.com/AndreasBriese/bbloom v0.0.0-20190306092124-e2d15f34fcf9 h1:HD8gA2tkByhMAwYaFAX9w2l7vxvBQ5NMoxDrkhqhtn4=
 github.com/AndreasBriese/bbloom v0.0.0-20190306092124-e2d15f34fcf9/go.mod h1:bOvUY6CB00SOBii9/FifXqc0awNKxLFCL/+pkDPuyl8=
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@@ -13,13 +14,17 @@ github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwc
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 github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/ethereum/go-ethereum v1.9.1 h1:MrdTRvKIa3apdx6NW1azzSgl8BQB1eTBVSUmFhuztaU=
 github.com/ethereum/go-ethereum v1.9.1/go.mod h1:PwpWDrCLZrV+tfrhqqF6kPknbISMHaJv9Ln3kPCZLwY=
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+github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
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 github.com/gdamore/tcell v1.2.0 h1:ikixzsxc8K8o3V2/CEmyoEW8mJZaNYQQ3NP3VIQdUe4=
@@ -29,26 +34,35 @@ github.com/go-zeromq/zmq4 v0.5.0 h1:DijriKlrr2b48mymvAsZApiPzrbxQodYKG1aDH1rz8c=
 github.com/go-zeromq/zmq4 v0.5.0/go.mod h1:6p7pjNlkfrQQVipmEuZDk7fakLZCqPPVK+Iq3jfbDg8=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.3.2 h1:6nsPYzhq5kReh6QImI3k5qWzO4PEbvbIW2cwSfR/6xs=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/open-location-code/go v0.0.0-20190723034300-2c7115db77a3 h1:qI8YeX4bVZ2HrE+kEOn12L2io7Tw/2IffULguAh3M4Q=
 github.com/google/open-location-code/go v0.0.0-20190723034300-2c7115db77a3/go.mod h1:eJfRN6aj+kR/rnua/rw9jAgYhqoMHldQkdTi+sePRKk=
+github.com/gorilla/websocket v1.4.0 h1:WDFjx/TMzVgy9VdMMQi2K2Emtwi2QcUQsztZ/zLaH/Q=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
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+github.com/mattn/go-isatty v0.0.8 h1:HLtExJ+uU2HOZ+wI0Tt5DtUDrx8yhUqDcp7fYERX4CE=
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@@ -57,6 +71,7 @@ github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+W
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 github.com/rivo/tview v0.0.0-20190721135419-23dc8a0944e4 h1:3L7UVoI/26LdSEPadEc4tNPMW+4vLBJaj31jAlJG4xg=
@@ -77,7 +92,9 @@ github.com/stretchr/objx v0.2.0/go.mod h1:qt09Ya8vawLte6SNmTgCsAVtYtaKzEcn8ATUoH
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
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plugins/dashboard/tps.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"html/template"
 	"net/http"
+	"sync"
 
 	"github.com/gorilla/websocket"
 	"github.com/iotaledger/goshimmer/packages/events"
@@ -25,8 +26,13 @@ func ServeWs(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	var websocketWriteMutex sync.Mutex
+
 	notifyWebsocketClient := events.NewClosure(func(sampledTPS uint64) {
 		go func() {
+			websocketWriteMutex.Lock()
+			defer websocketWriteMutex.Unlock()
+
 			p := make([]byte, 4)
 			binary.LittleEndian.PutUint32(p, uint32(sampledTPS))
 			if err := ws.WriteMessage(websocket.BinaryMessage, p); err != nil {