To this day (8/8/2019) Terraform is not packaged in an official apt repository. There is an option to install it with Snap but be careful it will probably be an older version. When i checked it was v0.11.11
If you do want to install it with snap, run:
$ snap install terraform
To install the latest version follow this procedure.
You might want to update your system just in case:
$ sudo apt-get update
Now since you are getting a Terraform binary from official Hashicorp site, you will need both wget and unzip packages unless already installed:
$ sudo apt-get install wget unzip
Last step would be to download an unzip Terraform package (you can find latest here).
$ wget https://releases.hashicorp.com/terraform/0.12.6/terraform_0.12.6_linux_amd64.zip
$ sudo unzip ./terraform_0.12.6_linux_amd64.zip -d /usr/local/bin/
check that it is installed:
$ terraform -v
you are all done.
Provided by:Forthscale systems, cloud experts