update readme

README.md

@@ -120,7 +120,7 @@ Access control is via the ZeroTier control interface itself and `metricstoken.se
     curl -H "X-ZT1-Auth: $(sudo cat /var/lib/zerotier-one/metricstoken.secret)" http://localhost:9993/metrics
 
     // macOS
-    curl -H "X-XT1-Auth: $(sudo cat /Library/Application\ Support/ZeroTier/One/metricstoken.secret)" http://localhost:9993/metrics
+    curl -H "X-ZT1-Auth: $(sudo cat /Library/Application\ Support/ZeroTier/One/metricstoken.secret)" http://localhost:9993/metrics
 
     // Windows PowerShell (Admin)
     Invoke-RestMethod -Headers @{'X-ZT1-Auth' = "$(Get-Content C:\ProgramData\ZeroTier\One\metricstoken.secret)"; } -Uri http://localhost:9993/metrics