better doc for interfaces

internal/db/db.go

@@ -7,9 +7,18 @@ import (
 )
 
 type DB interface {
+	// Return nil if share does not exist
 	GetShare(ctx context.Context, slug string) (*types.Share, error)
+
+	// Returns error if share already exists
 	CreateShare(ctx context.Context, share *types.Share) error
+
+	// Returns error if share does not exist
 	DeleteShare(ctx context.Context, slug string) error
+
+	// Returns all shares
 	GetAllShares(ctx context.Context) ([]*types.Share, error)
+
+	// Close the database
 	Close() error
 }