I encountered this error below after running

eval $(minikube docker-env)
docker ps

error during connect: Get 
https://192.168.99.181:2376/v1.40/containers/json: x509: certificate signed 
by unknown authority

Here is some details when I ran

minikube docker-env

export DOCKER_TLS_VERIFY="1"  
export DOCKER_HOST="tcp://192.168.99.181:2376"  
export DOCKER_CERT_PATH="/Users/myuser.name/.minikube/certs"

I am using MACOS.