web.config を次のように書き換えます

<aspNetCore processPath="dotnet" arguments=".\TestLoginApp5.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" />

<aspNetCore processPath="dotnet" arguments=".\TestLoginApp5.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout">
	<environmentVariables>
	<environmentVariable name="ASPNETCORE_ENVIRONMENT" value="Development" />
	</environmentVariables>
</aspNetCore>