implement basic fetchers

Sources/Conf/Fetcher.swift

@@ -0,0 +1,19 @@
+import Foundation
+
+/// Namespace for the predefined fetchers
+enum Fetcher { }
+
+extension Fetcher {
+    
+    static let direct: (Data) -> CommonConfigurationProvider.Fetcher = { data in
+       return { data }
+    }
+
+    static let file: (String) -> CommonConfigurationProvider.Fetcher = { configName in
+        return {
+            let url = URL(fileURLWithPath: configName, isDirectory: false)
+            print(url)
+            return try Data(contentsOf: url)
+        }
+    }
+}

Tests/ConfTests/FileFetcherTests.swift

@@ -0,0 +1,14 @@
+import XCTest
+@testable import Conf
+
+final class FileFetcherTests: XCTestCase {
+    func testSuccess() throws {
+        let load = Fetcher.file("Tests/Resources/valid.env")
+        _ = try load()
+    }
+
+    func testError() throws {
+        let load = Fetcher.file("file that not exist")
+        XCTAssertThrowsError(try load())
+    }
+}