add core lib

dotenv/dotenv.go

@@ -0,0 +1,52 @@
+package config
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+// LoadDotEnvCandidates loads KEY=VALUE pairs from the first existing file in paths.
+// Existing process env vars are preserved (file values only fill missing keys).
+func LoadDotEnvCandidates(paths []string) {
+	for _, path := range paths {
+		if loadDotEnvFile(path) {
+			return
+		}
+	}
+}
+
+func loadDotEnvFile(path string) bool {
+	file, err := os.Open(path)
+	if err != nil {
+		return false
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		key, value, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+
+		key = strings.TrimSpace(key)
+		value = strings.TrimSpace(value)
+		value = strings.Trim(value, `"'`)
+		if key == "" {
+			continue
+		}
+
+		if _, exists := os.LookupEnv(key); exists {
+			continue
+		}
+		_ = os.Setenv(key, value)
+	}
+
+	return true
+}