Load a Visualforce Page with Parameters in Lightning – UnofficialSF

<aura:component implements="flexipage:availableForAllPageTypes,force:hasRecordId" access="global">

    <lightning:workspaceAPI aura:id="workspace" />

    <aura:attribute name="buttonLabel" type="String" />
    <aura:attribute name="buttonVariant" type="String" default="neutral" />
    <aura:attribute name="domain" type="String" />
    <aura:attribute name="pageName" type="String" />
    <aura:attribute name="recordIdVar" type="String" />
    <aura:attribute name="otherParams" type="String" />

    <aura:attribute name="queryString" type="String" />

    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />

    <lightning:card>
        <lightning:layoutItem padding="around-small">
            <lightning:button label="{!v.buttonLabel}" variant="{!v.buttonVariant}" onclick="{!c.openPage}" />
            <lightning:spinner aura:id="spinner" alternativeText="Loading" variant="brand" size="large" class="slds-hide" />
        </lightning:layoutItem>
    </lightning:card>

</aura:component>