add new os pkg on ocis-pkg

ocis-pkg/os/os.go

@@ -0,0 +1,17 @@
+package os
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// MustUserConfigDir generates a default config location for a user based on their OS. This location can be used to store
+// any artefacts the app needs for its functioning. It is a pure function. Its only side effect is that results vary
+// depending on which operative system we're in.
+func MustUserConfigDir(prefix, extension string) string {
+	dir, err := os.UserConfigDir()
+	if err != nil {
+		panic(err)
+	}
+	return filepath.Join(dir, prefix, extension)
+}

ocis-pkg/os/os_test.go

@@ -0,0 +1,36 @@
+package os
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func Test_mustUserConfigDir(t *testing.T) {
+	configDir, _ := os.UserConfigDir()
+	type args struct {
+		prefix    string
+		extension string
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "fetch the default config location for the current user",
+			args: args{
+				prefix:    "ocis",
+				extension: "testing",
+			},
+			want: filepath.Join(configDir, "ocis", "testing"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := MustUserConfigDir(tt.args.prefix, tt.args.extension); got != tt.want {
+				t.Errorf("MustUserConfigDir() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}