Added hclsecret package for using secrets in HCL files

hclsecret/example_test.go

@@ -0,0 +1,57 @@
+package hclsecret_test
+
+import (
+	"fmt"
+
+	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/hclsimple"
+	"github.com/zclconf/go-cty/cty/function"
+
+	"git.maze.io/go/secret/hclsecret"
+)
+
+type mockProvider struct {
+	out []byte
+	err error
+}
+
+func (p mockProvider) GetSecret(string) ([]byte, error) {
+	return p.out, p.err
+}
+
+func ExampleFunction() {
+	// p would be your initialized secret.Provider
+	p := mockProvider{[]byte("it works!"), nil}
+
+	// Our stand-in configuration file
+	b := []byte(`
+database {
+	username = "root"
+	password = secret("password")
+}
+`)
+
+	// Our stand-in configuration struct
+	type databaseConfig struct {
+		Username string `hcl:"username"`
+		Password string `hcl:"password"`
+	}
+
+	var config struct {
+		Database databaseConfig `hcl:"database,block"`
+	}
+
+	// HCL evaluation context
+	ctx := &hcl.EvalContext{
+		Functions: map[string]function.Function{
+			"secret": hclsecret.Function(p),
+		},
+	}
+
+	if err := hclsimple.Decode("example.hcl", []byte(b), ctx, &config); err != nil {
+		panic(err)
+	}
+
+	fmt.Println(config.Database.Password)
+	// Output: it works!
+}