[config] minor fixes to koanf usage

Author: capcom6

config/config.go

@@ -8,15 +8,17 @@ import (
 
 	"github.com/knadh/koanf/parsers/dotenv"
 	"github.com/knadh/koanf/parsers/yaml"
-	"github.com/knadh/koanf/providers/env"
+	"github.com/knadh/koanf/providers/env/v2"
 	"github.com/knadh/koanf/providers/file"
 	"github.com/knadh/koanf/providers/s3"
 	"github.com/knadh/koanf/v2"
 )
 
+var errMissingAWSCreds = errors.New("AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION must be set")
+
 // Load reads configuration from various sources and unmarshals it into a given struct.
 //
-// It looks for configuration in the following order:
+// It looks for configuration in the following order (later overrides earlier):
 // 1. S3, if `withS3` is provided.
 // 2. Local file, if `withYaml` is provided.
 // 3. `.env` file in the current working directory.
@@ -28,7 +30,7 @@ import (
 //
 // The final configuration will be unmarshaled into the given struct. If unmarshaling fails, an error will be returned.
 func Load[T any](c *T, opts ...Option) error {
-	options := &options{}
+	options := new(options)
 	options.apply(opts...)
 
 	k := koanf.New(".")
@@ -40,7 +42,7 @@ func Load[T any](c *T, opts ...Option) error {
 		endpoint := os.Getenv("AWS_ENDPOINT")
 
 		if accessKey == "" || secretKey == "" || region == "" {
-			return errors.New("AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION must be set")
+			return errMissingAWSCreds
 		}
 
 		s3Config := s3.Config{
@@ -70,7 +72,13 @@ func Load[T any](c *T, opts ...Option) error {
 		return fmt.Errorf("load dotenv: %w", err)
 	}
 
-	if err := k.Load(env.Provider("", "__", strings.ToLower), nil); err != nil {
+	if err := k.Load(env.Provider("__", env.Opt{
+		Prefix: "",
+		TransformFunc: func(k, v string) (string, any) {
+			return strings.ToLower(k), v
+		},
+		EnvironFunc: nil,
+	}), nil); err != nil {
 		return fmt.Errorf("load env: %w", err)
 	}
 

config/options.go

@@ -15,17 +15,17 @@ func (o *options) apply(opts ...Option) {
 	}
 }
 
-// WithLocalYaml specifies a path to a local YAML file to load config from.
+// WithLocalYAML specifies a path to a local YAML file to load config from.
 // If the file does not exist, an error is not returned.
-func WithLocalYaml(path string) Option {
+func WithLocalYAML(path string) Option {
 	return func(o *options) {
 		o.withYaml = path
 	}
 }
 
-// WithS3 specifies a path to a local YAML file to load config from.
-// If the file does not exist, an error is not returned.
-func WithS3(bucket string, objectKey string) Option {
+// WithS3YAML configures loading config from S3 (s3://<bucket>/<objectKey>).
+// If the object is missing, it is skipped without returning an error.
+func WithS3YAML(bucket string, objectKey string) Option {
 	return func(o *options) {
 		o.withS3Bucket = bucket
 		o.withS3ObjectKey = objectKey

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/gofiber/fiber/v2 v2.52.9
 	github.com/knadh/koanf/parsers/dotenv v1.1.0
 	github.com/knadh/koanf/parsers/yaml v1.1.0
-	github.com/knadh/koanf/providers/env v1.1.0
+	github.com/knadh/koanf/providers/env/v2 v2.0.0
 	github.com/knadh/koanf/providers/file v1.2.0
 	github.com/knadh/koanf/providers/s3 v1.0.0
 	github.com/knadh/koanf/v2 v2.2.2

go.sum

@@ -40,8 +40,8 @@ github.com/knadh/koanf/parsers/dotenv v1.1.0 h1:dQaM0Jw54zRsqDcaJ27pciNExuKfOXag
 github.com/knadh/koanf/parsers/dotenv v1.1.0/go.mod h1:P3BQjxaIc2+SZ3n9BUceqYl95pz3qaGqYTZX0j0d/DI=
 github.com/knadh/koanf/parsers/yaml v1.1.0 h1:3ltfm9ljprAHt4jxgeYLlFPmUaunuCgu1yILuTXRdM4=
 github.com/knadh/koanf/parsers/yaml v1.1.0/go.mod h1:HHmcHXUrp9cOPcuC+2wrr44GTUB0EC+PyfN3HZD9tFg=
-github.com/knadh/koanf/providers/env v1.1.0 h1:U2VXPY0f+CsNDkvdsG8GcsnK4ah85WwWyJgef9oQMSc=
-github.com/knadh/koanf/providers/env v1.1.0/go.mod h1:QhHHHZ87h9JxJAn2czdEl6pdkNnDh/JS1Vtsyt65hTY=
+github.com/knadh/koanf/providers/env/v2 v2.0.0 h1:Ad5H3eun722u+FvchiIcEIJZsZ2M6oxCkgZfWN5B5KY=
+github.com/knadh/koanf/providers/env/v2 v2.0.0/go.mod h1:1g01PE+Ve1gBfWNNw2wmULRP0tc8RJrjn5p2N/jNCIc=
 github.com/knadh/koanf/providers/file v1.2.0 h1:hrUJ6Y9YOA49aNu/RSYzOTFlqzXSCpmYIDXI7OJU6+U=
 github.com/knadh/koanf/providers/file v1.2.0/go.mod h1:bp1PM5f83Q+TOUu10J/0ApLBd9uIzg+n9UgthfY+nRA=
 github.com/knadh/koanf/providers/s3 v1.0.0 h1:VYzH2B+/pxO2WGGPV0l7ANfYSl0Q6lLkseEiGjGTNz8=