Templates

omnimail.Template renders a subject, a plain-text body and an HTML body from one data value.

Safe Defaults

• The HTML body uses html/template: data is escaped for its context, and unsafe URLs (for example javascript:) are replaced with #ZgotmplZ.
• The subject and text body use text/template.
• A missing map key is an error (missingkey=error) instead of <no value>.
• The rendered subject is collapsed to one line (control characters and whitespace runs become single spaces), so template data cannot inject headers.

From Strings

tmpl, err := omnimail.ParseTemplate("verify", omnimail.TemplateSource{
    Subject: "Verify your {{.Product}} email",
    Text:    "Hi {{.Name}},\n\nOpen this link to verify: {{.Link}}\n",
    HTML:    `<p>Hi {{.Name}},</p><p><a href="{{.Link}}">Verify your email</a></p>`,
})

From Files (embed.FS)

ParseTemplateFS(fsys, name) reads name.subject.tmpl, name.text.tmpl and name.html.tmpl. Missing files are skipped, but a text or HTML body is required.

mail/
├── verify.subject.tmpl
├── verify.text.tmpl
└── verify.html.tmpl

//go:embed mail/*.tmpl
var mailFS embed.FS

tmpl, err := omnimail.ParseTemplateFS(mailFS, "mail/verify")

Rendering

data := map[string]any{"Product": "Acme", "Name": user.Name, "Link": link}

// Render returns the three parts.
r, err := tmpl.Render(data) // r.Subject, r.Text, r.HTML

// Apply sets Subject (when the template has one), Text and HTML on a message.
msg := &omnimail.Message{From: from, To: []omnimail.Address{to}}
if err := tmpl.Apply(msg, data); err != nil {
    return err
}

Options

omnimail.ParseTemplate("x", src,
    omnimail.WithFuncs(map[string]any{"upper": strings.ToUpper}),
    omnimail.WithDelims("[[", "]]"),
)

Parse templates once at startup and reuse them; a Template is safe for concurrent Render calls.