[FIX] Formatting and code-style (#118)

* [FIX] Formatting and code-style

- gofmt
- import resort
- prealloc slices
- simplify code

* fix vet

pkg/network/server_test.go

@@ -28,7 +28,9 @@ func TestSendVersion(t *testing.T) {
 		assert.Equal(t, uint32(0), version.StartHeight)
 	}
 
-	s.sendVersion(p)
+	if err := s.sendVersion(p); err != nil {
+		t.Fatal(err)
+	}
 }
 
 // Server should reply with a verack after receiving a valid version.