I had the same problem, i solved it like this:
First, change the package.swift like this: (In fact, this is the same as WWDC Session)
// swift-tools-version: 5.7
import PackageDescription
let package = Package(
name: "MyServer",
platforms: [.macOS("12.0")],
products: [
.executable(
name: "MyServer",
targets: ["MyServer"]),
],
dependencies: [
.package(url: "https://github.com/vapor/vapor.git", .upToNextMajor(from: "4.0.0")),
],
targets: [
.executableTarget(
name: "MyServer",
dependencies: [
.product(name: "Vapor", package: "vapor")
]),
.testTarget(
name: "MyServerTests",
dependencies: ["MyServer"]),
]
)
Second, Find Executable menu with action Edit Scheme -> Run -> info, open the menu, you will find the target you added in Package.swift.
Hope this helps !