Push the RunMode setting out to its own attribute, because fox wants consistency.

Bonus: Removes the need for that godawful 'RunMode.Default'.

src/Discord.Net.Commands/Attributes/CommandAttribute.cs

@@ -6,7 +6,6 @@ namespace Discord.Commands
     public class CommandAttribute : Attribute
     {
         public string Text { get; }
-        public RunMode RunMode { get; set; } = RunMode.Default;
 
         public CommandAttribute()
         {

src/Discord.Net.Commands/Attributes/SetRunModeAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Discord.Commands
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public sealed class SetRunModeAttribute : Attribute
+    {
+        public RunMode RunMode { get; }
+
+        public SetRunModeAttribute(RunMode runMode)
+        {
+            RunMode = runMode;
+        }
+    }
+}

src/Discord.Net.Commands/Builders/ModuleBuilder.cs

@@ -20,6 +20,7 @@ namespace Discord.Commands.Builders
         public string Remarks { get; set; }
         public string Group { get; set; }
         public bool IgnoreExtraArgs { get; set; }
+        public RunMode RunMode { get; set; }
 
         public IReadOnlyList<CommandBuilder> Commands => _commands;
         public IReadOnlyList<ModuleBuilder> Modules => _submodules;
@@ -35,6 +36,7 @@ namespace Discord.Commands.Builders
             Service = service;
             Parent = parent;
             IgnoreExtraArgs = service._ignoreExtraArgs;
+            RunMode = service._defaultRunMode;
 
             _commands = new List<CommandBuilder>();
             _submodules = new List<ModuleBuilder>();

src/Discord.Net.Commands/Builders/ModuleClassBuilder.cs

@@ -126,6 +126,9 @@ namespace Discord.Commands
                     case IgnoreExtraArgsAttribute ignoreExtra:
                         builder.IgnoreExtraArgs = ignoreExtra.IgnoreValue;
                         break;
+                    case SetRunModeAttribute runmode:
+                        builder.RunMode = runmode.RunMode;
+                        break;
                     default:
                         builder.AddAttributes(attribute);
                         break;
@@ -159,7 +162,6 @@ namespace Discord.Commands
                 {
                     case CommandAttribute command:
                         builder.AddAliases(command.Text);
-                        builder.RunMode = command.RunMode;
                         builder.Name = builder.Name ?? command.Text;
                         break;
                     case NameAttribute name:
@@ -183,6 +185,9 @@ namespace Discord.Commands
                     case IgnoreExtraArgsAttribute ignoreExtra:
                         builder.IgnoreExtraArgs = ignoreExtra.IgnoreValue;
                         break;
+                    case SetRunModeAttribute runmode:
+                        builder.RunMode = runmode.RunMode;
+                        break;
                     default:
                         builder.AddAttributes(attribute);
                         break;

src/Discord.Net.Commands/CommandService.cs

@@ -45,8 +45,6 @@ namespace Discord.Commands
             _ignoreExtraArgs = config.IgnoreExtraArgs;
             _separatorChar = config.SeparatorChar;
             _defaultRunMode = config.DefaultRunMode;
-            if (_defaultRunMode == RunMode.Default)
-                throw new InvalidOperationException("The default run mode cannot be set to Default.");
 
             _logManager = new LogManager(config.LogLevel);
             _logManager.Message += async msg => await _logEvent.InvokeAsync(msg).ConfigureAwait(false);

src/Discord.Net.Commands/Info/CommandInfo.cs

@@ -43,7 +43,7 @@ namespace Discord.Commands
             Summary = builder.Summary;
             Remarks = builder.Remarks;
 
-            RunMode = (builder.RunMode == RunMode.Default ? service._defaultRunMode : builder.RunMode);
+            RunMode = builder.RunMode;
             Priority = builder.Priority;
 
             Aliases = module.Aliases

src/Discord.Net.Commands/Info/ModuleInfo.cs

@@ -14,6 +14,7 @@ namespace Discord.Commands
         public string Remarks { get; }
         public string Group { get; }
         public bool IgnoreExtraArgs { get; }
+        public RunMode RunMode { get; }
 
         public IReadOnlyList<string> Aliases { get; }
         public IReadOnlyList<CommandInfo> Commands { get; }
@@ -32,6 +33,7 @@ namespace Discord.Commands
             Remarks = builder.Remarks;
             Group = builder.Group;
             IgnoreExtraArgs = builder.IgnoreExtraArgs;
+            RunMode = builder.RunMode;
             Parent = parent;
 
             Aliases = BuildAliases(builder, service).ToImmutableArray();

src/Discord.Net.Commands/RunMode.cs

@@ -1,8 +1,7 @@
-namespace Discord.Commands
+namespace Discord.Commands
 {
     public enum RunMode
     {
-        Default,
         Sync,
         Async
     }