Package opencv4 was not found in the pkg-config search path

[kabukky]

I've followed the installation steps on macOS.

• Go is at the newest version (go version go1.12.9 darwin/amd64).
• opencv: stable 4.1.1 (bottled)

Still, I get this error:

go run ./cmd/version/main.go
# pkg-config --cflags  -- opencv4
Package opencv4 was not found in the pkg-config search path.
Perhaps you should add the directory containing `opencv4.pc'
to the PKG_CONFIG_PATH environment variable
No package 'opencv4' found
pkg-config: exit status 1

I've also tried using the dev branch, still the same error.