so I have installed SFT4 toolchain / and configured xcode toolchain / and terminal
(base) โ ~ export SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk
export PATH=/Library/Developer/Toolchains/swift-tensorflow-RELEASE-0.3.1.xctoolchain/usr/bin:$PATH
(base) โ ~ which swift
/Library/Developer/Toolchains/swift-tensorflow-RELEASE-0.3.1.xctoolchain/usr/bin/swift