1. CREATE YOUR SSH KEYS
First you need to create your two ssh key

  >> ssh-keygen -t rsa -C "test1@test.com"
  >> ssh-keygen -t rsa -f ~/.ssh/id_rsa_OTHER_LABEL -C "test2@test.com"

<b>Note:</b> You can use anyname for your public second key


2. ATTACH THE GITHUB KEYS

login in each github account and attach your keys respectively.
What do you gonna attach ?

  >> vim ~/.ssh/id_rsa[YOUR_NAME].pub
copy and paste into the public key field at github page

3. CREATE A CONFIG FILE
Well, we create two differents ssh keys and attach respectively in github.
Now, we have to create a way to identify the differents github accounts.

  Create a config file
  >> touch ~/.ssh/config
  >> vim ~/.ssh/config

example:

#Default GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa
#Default GitHub
Host github-company
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa_OTHER_LABEL

and save the changes.

4. HOW IT WORKS?

Now, if you wanna create new project, you have to specify the HOST name in the
add remote origin step change.

Example
 git init
 git commit -m"firt commit"
#now if you use your first one ( normal github )
 git remote add origin git@github.com:Company/testing.git
#instead it you want to use the other user just change the HOST name
 git remote add origin git@github-COMPANY:Company/testing.git

:)