Go cannot find packages in go/pkg looking in go/src

trying to work with GoLang and MQTT but go seems unable to find the packages.

% go version
go version go1.16.7 darwin/amd64

foobar.go

package main

import (
	"fmt"
	"log"
	"os/exec"
	"time"
	mqtt "github.com/eclipse/paho.mqtt.golang"
)

when trying to run I would get the following error

go run foobar.go
foobar.go:9:2: no required module provides package github.com/eclipse/paho.mqtt.golang: go.mod file not found in current directory or any parent directory; see 'go help modules'

% go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/{user}/Library/Caches/go-build"
GOENV="/Users/{user}/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/{user}/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/{user}/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.16.7"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/rg/80kn_qfn0_91cv0_fb43_m5r0000gn/T/go-build2547135435=/tmp/go-build -gno-record-gcc-switches -fno-common"

I set $GOPATH and $GOROOT to match the go env. I even tried going back to the old path method by setting GO111MODULE="off", but that resulted in this error

% go run foobar.go
foobar.go:8:2: cannot find package "github.com/eclipse/paho.mqtt.golang" in any of:
	/usr/local/go/src/github.com/eclipse/paho.mqtt.golang (from $GOROOT)
	/Users/{user}/go/src/github.com/eclipse/paho.mqtt.golang (from $GOPATH)

I am confused because go get/install github.com/eclipse/paho.mqtt.golang appears to be installing of my packages are being installed under go/pkg/ while the above output and all the documentation I read says indicated the /src so why do I have the /pkg directory.

Please use modules. You should not be setting GOROOT or GOPATH.

I recommend going through the following path, using official documentation pages:

1. Read about properly installing Go for your platform.
2. Read the getting started tutorial which also tells you how to install 3rd-party packages and use them in your code.

It should take you no more than 20 minutes to go through these steps, and it's almost certain that you'll be able to accomplish your goal by the end of the process. As a bonus, keep going through the Getting Started guide beyond the first page to learn how to create your own Go modules, use them from other modules, write tests, build your code into a binary, and more.

This is IMHO the minimal background required to even try writing Go programs; without going through these steps, you will lack crucial fundamental understanding and it will be hard to even understand SO answers.