<span onkeypress="{!c.keyCheck}" class="slds-size--11-of-12 input-field">
            <lightning:textarea aura:id="inputField"
                                maxLength="160"
                                label=""
                                name="inputField"
                                placeholder="Type message, press RETURN to send..."
                                value="{!v.MessageInput}"/>
        </span>

component.find("inputField").focus();