add TSamFailedOnly command and change test output within the floating window

tests/test_samurai_go_spec.lua

@@ -95,7 +95,7 @@ describe("test-samurai go runner", function()
 
     local cmd_spec_sub = go_runner.build_command(spec_sub)
     assert.are.same(
-      { "go", "test", "-v", "./pkg", "-run", "^TestFoo/first$" },
+      { "go", "test", "-json", "./pkg", "-run", "^TestFoo/first$" },
       cmd_spec_sub.cmd
     )
 
@@ -108,7 +108,7 @@ describe("test-samurai go runner", function()
 
     local cmd_spec_func = go_runner.build_command(spec_func)
     assert.are.same(
-      { "go", "test", "-v", "./", "-run", "^TestFoo($|/)" },
+      { "go", "test", "-json", "./", "-run", "^TestFoo($|/)" },
       cmd_spec_func.cmd
     )
   end)