Error: Failed to start OmniSharp MacOS

Error during OmniSharp startup on MacOS. Please let me know if you need more information.

    Target: /Users/<USER>/development/tmp/csplay/csplay.sln

OmniSharp server started with Mono 5.18.1.
    Path: /Users/<USER>/.vscode/extensions/ms-vscode.csharp-1.20.0/.omnisharp/1.32.20/omnisharp/OmniSharp.exe
    PID: 59159

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on MacOS 10.14.5 (x64)
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Located 2 MSBuild instance(s)
            1: Mono 15.0 - "/Library/Frameworks/Mono.framework/Versions/5.18.1/lib/mono/msbuild/15.0/bin"
            2: StandAlone 15.0 - "/Users/<USER>/.vscode/extensions/ms-vscode.csharp-1.20.0/.omnisharp/1.32.20/omnisharp/.msbuild/Current/Bin"
[info]: OmniSharp.MSBuild.Discovery.MSBuildLocator
        Registered MSBuild instance: Mono 15.0 - "/Library/Frameworks/Mono.framework/Versions/5.18.1/lib/mono/msbuild/15.0/bin"
            CscToolPath = /Users/<USER>/.vscode/extensions/ms-vscode.csharp-1.20.0/.omnisharp/1.32.20/omnisharp/.msbuild/Current/Bin/Roslyn
            CscToolExe = csc.exe
System.InvalidOperationException: Failed to convert 'null' to type 'System.Int32'. ---> System.ArgumentException: null is not a valid value for Int32.
Parameter name: value ---> System.FormatException: Input string was not in a correct format.
  at System.Number.StringToNumber (System.ReadOnlySpan`1[T] str, System.Globalization.NumberStyles options, System.Number+NumberBuffer& number, System.Globalization.NumberFormatInfo info, System.Boolean parseDecimal) [0x00045] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.Number.ParseInt32 (System.ReadOnlySpan`1[T] s, System.Globalization.NumberStyles style, System.Globalization.NumberFormatInfo info) [0x0000a] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.Int32.Parse (System.String s, System.Globalization.NumberStyles style, System.IFormatProvider provider) [0x0001d] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.ComponentModel.Int32Converter.FromString (System.String value, System.Globalization.NumberFormatInfo formatInfo) [0x00000] in <118907f5eb5f4e538f3e3bdd8361378f>:0 
  at System.ComponentModel.BaseNumberConverter.ConvertFrom (System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.Object value) [0x00092] in <118907f5eb5f4e538f3e3bdd8361378f>:0 
   --- End of inner exception stack trace ---
  at System.ComponentModel.BaseNumberConverter.ConvertFrom (System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.Object value) [0x000bf] in <118907f5eb5f4e538f3e3bdd8361378f>:0 
  at System.ComponentModel.TypeConverter.ConvertFromString (System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, System.String text) [0x00000] in <118907f5eb5f4e538f3e3bdd8361378f>:0 
  at System.ComponentModel.TypeConverter.ConvertFromInvariantString (System.String text) [0x00007] in <118907f5eb5f4e538f3e3bdd8361378f>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.TryConvertValue (System.Type type, System.String value, System.Object& result, System.Exception& error) [0x00073] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
   --- End of inner exception stack trace ---
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance (System.Type type, System.Object instance, Microsoft.Extensions.Configuration.IConfiguration config, Microsoft.Extensions.Configuration.BinderOptions options) [0x0003a] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindProperty (System.Reflection.PropertyInfo property, System.Object instance, Microsoft.Extensions.Configuration.IConfiguration config, Microsoft.Extensions.Configuration.BinderOptions options) [0x0007c] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar (Microsoft.Extensions.Configuration.IConfiguration configuration, System.Object instance, Microsoft.Extensions.Configuration.BinderOptions options) [0x00021] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance (System.Type type, System.Object instance, Microsoft.Extensions.Configuration.IConfiguration config, Microsoft.Extensions.Configuration.BinderOptions options) [0x000d1] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindProperty (System.Reflection.PropertyInfo property, System.Object instance, Microsoft.Extensions.Configuration.IConfiguration config, Microsoft.Extensions.Configuration.BinderOptions options) [0x0007c] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindNonScalar (Microsoft.Extensions.Configuration.IConfiguration configuration, System.Object instance, Microsoft.Extensions.Configuration.BinderOptions options) [0x00021] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.BindInstance (System.Type type, System.Object instance, Microsoft.Extensions.Configuration.IConfiguration config, Microsoft.Extensions.Configuration.BinderOptions options) [0x000d1] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Configuration.ConfigurationBinder.Bind (Microsoft.Extensions.Configuration.IConfiguration configuration, System.Object instance, System.Action`1[T] configureOptions) [0x00027] in <5b476e36d7ed40118121c30cde0aa9a7>:0 
  at Microsoft.Extensions.Options.NamedConfigureFromConfigurationOptions`1+<>c__DisplayClass1_0[TOptions].<.ctor>b__0 (TOptions options) [0x00000] in <d2497bba08e44fd8883919a01afaf5eb>:0 
  at Microsoft.Extensions.Options.ConfigureNamedOptions`1[TOptions].Configure (System.String name, TOptions options) [0x00033] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at Microsoft.Extensions.Options.OptionsFactory`1[TOptions].Create (System.String name) [0x00025] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at Microsoft.Extensions.Options.OptionsMonitor`1+<>c__DisplayClass10_0[TOptions].<Get>b__0 () [0x00000] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at System.Lazy`1[T].ViaFactory (System.Threading.LazyThreadSafetyMode mode) [0x00043] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.Lazy`1[T].ExecutionAndPublication (System.LazyHelper executionAndPublication, System.Boolean useDefaultConstructor) [0x00022] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.Lazy`1[T].CreateValue () [0x00074] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at System.Lazy`1[T].get_Value () [0x0000a] in <b4d1a66727f44ba888b54966284fabb4>:0 
  at Microsoft.Extensions.Options.OptionsCache`1[TOptions].GetOrAdd (System.String name, System.Func`1[TResult] createOptions) [0x0002c] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at Microsoft.Extensions.Options.OptionsMonitor`1[TOptions].Get (System.String name) [0x00029] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at Microsoft.Extensions.Options.OptionsMonitor`1[TOptions].get_CurrentValue () [0x00000] in <87daea5cc5d047d4a6bbff8954aa1c4a>:0 
  at OmniSharp.CompositionHostBuilder.Build () [0x000ed] in <68c5db2d7e5646be8800d2236f54f97e>:0 
  at OmniSharp.Stdio.Host..ctor (System.IO.TextReader input, OmniSharp.Services.ISharedTextWriter writer, OmniSharp.IOmniSharpEnvironment environment, System.IServiceProvider serviceProvider, OmniSharp.CompositionHostBuilder compositionHostBuilder, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, System.Threading.CancellationTokenSource cancellationTokenSource) [0x00057] in <3c66497ecf1345b2b9aed9f29cd4f8d6>:0 
  at OmniSharp.Stdio.Driver.Program+<>c__DisplayClass0_1.<Main>b__1 () [0x00138] in <87b189b95abd49d7a5b690d199a0ecee>:0 
  at OmniSharp.CommandLineApplication+<>c__DisplayClass11_0.<OnExecute>b__0 () [0x0000b] in <68c5db2d7e5646be8800d2236f54f97e>:0 
  at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute (System.String[] args) [0x00039] in <344a1e8cd6594b17b1e01f8df6ae8827>:0 
  at OmniSharp.CommandLineApplication.Execute (System.Collections.Generic.IEnumerable`1[T] args) [0x00042] in <68c5db2d7e5646be8800d2236f54f97e>:0 
  at OmniSharp.Stdio.Driver.Program+<>c__DisplayClass0_0.<Main>b__0 () [0x00028] in <87b189b95abd49d7a5b690d199a0ecee>:0 
  at OmniSharp.HostHelpers.Start (System.Func`1[TResult] action) [0x0001c] in <68c5db2d7e5646be8800d2236f54f97e>:0 
[ERROR] Error: OmniSharp server load timed out. Use the 'omnisharp.projectLoadTimeout' setting to override the default delay (one minute).```

[filipw]

thanks. are you using a custom omnisharp.json file? if so, please share it too. Also, can you post the contents of your settings.json (the VS Code settings file).

[accidentalentomologist]

Thanks @filipw and @akshita31 for your help.

It turns out the error was in the settings.json file. For some reason tabSize was set to null: "editor.tabSize": null,

Changing that to a more appropriate value fixed the issue