updated publish to NuGet script

publish.ps1

@@ -1,5 +1,12 @@
 # publishes to NuGet
 # $apiKey needs to be already set up with NuGet publishing key
+Write-Host $PSScriptRoot
+
+if (-not $apiKey)
+{
+    throw "Need to set the API key first"
+}
+
 $packages = "NAudio.Core", "NAudio.Asio", "NAudio.WinForms", "NAudio.Midi", 
             "NAudio.WinMM", "NAudio.Wasapi", "NAudio.Uap",
             "NAudio", "NAudio.Extras"
@@ -7,9 +14,11 @@ $packages = "NAudio.Core", "NAudio.Asio", "NAudio.WinForms", "NAudio.Midi",
 foreach ($package in $packages)
 {
     # publish the most recently created .nupkg file
-    $folder = "$package\bin\Release"
+    $folder = "$PSScriptRoot\$package\bin\Release"
     $recent = gci "$folder\*.nupkg" | sort LastWriteTime | select -last 1
     $pkg = $recent.Name
     # note that this will fail with 409 error if you try to push package that already exists
-    dotnet nuget push "$folder\$pkg" --api-key $apiKey --source https://api.nuget.org/v3/index.json
+    Write-Host "publishing $pkg"
+    dotnet nuget push "$folder\$pkg" --api-key $apiKey --source https://api.nuget.org/v3/index.json | out-null
+    if (-not $?) { Write-Error "Failed to publish $pkg" }
 }