Add Clibpq as a dependency in your Package.swift file:
// swift-tools-version:4.0 // The swift-tools-version declares the minimum version of Swift required to build this package. import PackageDescription let package = Package( name: "foo-bar", products: [ .executable(name: "foo-bar", targets: ["foo-bar"]), ], dependencies: [ .package(url: "https://github.com/ManuW/Clibpq", from: "0.0.3") ], targets: [ // Targets are the basic building blocks of a package. A target can define a module or a test suite. // Targets can depend on other targets in this package, and on products in packages which this package depends on. .target( name: "foo-bar", dependencies: [] ), ] )