Swift package manager documentation doesn’t show clearly how to make package depend on other package on local machine which is extreemly useful during development. Here is what you use: .package(url: "../swift-geometrize/", branch: "feature/asynciterator"). As alternative .package(path: "../Modules/MySwiftLib") could be used or its variant with package name .package(name: "MyPackage", path: "/local/path/to/package"). This .package(url: "file:///path/to/MySwiftLib", from: "1.0.0") technically is also possible but it is not too much useful during development. This is exert from package manifest which I use during development of geometrizebot:

let package = Package(
    name: "geometrizebot",
    platforms: [
    dependencies: [
        .package(url: "https://github.com/vapor/vapor.git", from: "4.76.0"),
        .package(url: "https://github.com/vapor/leaf", from: "4.2.4"),
        .package(url: "https://github.com/vapor/leaf-kit", from: "1.10.2"),
        .package(url: "https://github.com/nerzh/telegram-vapor-bot", from: "2.4.3"),
        //.package(url: "https://github.com/valeriyvan/swift-geometrize.git", from: "1.1.2"),
        .package(url: "../swift-geometrize/", branch: "feature/asynciterator"),
        .package(url: "https://github.com/valeriyvan/jpeg.git", from: "1.0.2"),
        .package(url: "https://github.com/kelvin13/swift-png.git", from: "4.0.2"),
        .package(url: "https://github.com/awslabs/aws-sdk-swift", exact: "0.17.0")