Add ability to load database env from file

internal/config/database.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"strconv"
+	"strings"
 )
 
 // Database holds the configuration data for setting up a connection to a
@@ -17,6 +18,25 @@ type Database struct {
 	SSLMode  string
 }
 
+func loadPassword() (string, error) {
+	password, ok := os.LookupEnv("POSTGRES_PASSWORD")
+	if ok {
+		return password, nil
+	}
+
+	passwordFile, ok := os.LookupEnv("POSTGRES_PASSWORD_FILE")
+	if !ok {
+		return "", fmt.Errorf("no POSTGRES_PASSWORD or POSTGRES_PASSWORD_FILE env var set")
+	}
+
+	data, err := os.ReadFile(passwordFile)
+	if err != nil {
+		return "", fmt.Errorf("failed to read from password file: %w", err)
+	}
+
+	return strings.TrimSpace(string(data)), nil
+}
+
 // NewDatabase creates a database configuration based on the environment
 // variables required. If any env variables are not set or are invalid then
 // this method will throw an error.
@@ -26,9 +46,9 @@ func NewDatabase() (*Database, error) {
 		return nil, fmt.Errorf("no POSTGRES_USER env variable set")
 	}
 
-	password, ok := os.LookupEnv("POSTGRES_PASSWORD")
-	if !ok {
-		return nil, fmt.Errorf("no POSTGRES_PASSWORD env variable set")
+	password, err := loadPassword()
+	if err != nil {
+		return nil, fmt.Errorf("loading password: %w", err)
 	}
 
 	host, ok := os.LookupEnv("POSTGRES_HOST")

internal/config/database_test.go

@@ -72,7 +72,7 @@ func TestCreatingNewValidation(t *testing.T) {
 				os.Unsetenv("POSTGRES_PASSWORD")
 			},
 			ExpectedErr: fmt.Errorf(
-				"no POSTGRES_PASSWORD env variable set",
+				"loading password: no POSTGRES_PASSWORD or POSTGRES_PASSWORD_FILE env var set",
 			),
 		},
 		{